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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Evolution of a HotRod - Part 4 Carburetor /cgi-bin/YaBB.pl?num=1625732492 Message started by DragBikeMike on 07/08/21 at 01:21:32 |
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Title: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:21:32 Evolution of a Hot Rod – Part 4 Carburetor & Air Filter (Revisited) This is the fourth in a series of reports intended to document the results of progressive modifications to the LS650 engine. Part 1 outlined the project, set the rules, and established the baseline performance values for a box-stock LS650. You can find Part 1 here. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1620523526 Part 2 examined the airbox. We improved performance dramatically with a few simple and inexpensive modifications. It was a lot of bang for the bucks. You can find Part 2 here. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1621150483 Part 3 took a hard look at the exhaust system. We tried a Dyna muffler and a hybrid muffler that I manufactured. We also tried the larger Mac header pipe. The exhaust modifications provided significant improvements in acceleration and fuel economy. You can find part 3 here. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1623048749 Part 4 installs a performance carburetor and revisits the air filter. As I tested the carburetor the air filter proved troublesome. I was compelled to take another look. What I am about to describe worked good for me. If you decide to try this stuff on your own, you assume responsibility for the outcome. If you don’t have the skills, don’t do it. If you don’t understand something, STOP and get help. Get a manual. Read up. Comply with ALL the safety requirements outlined in the manual. Make sure you know what you are doing before attempting any of this stuff. Let’s get started. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:23:11 As discussed in part 2, it’s all about air. If you want more power, you need more air. Logic dictates that a larger carburetor will allow more airflow into the engine, and that additional air should result in more power. There are limits. Get carried away with the carburetor and you end up with an engine that only makes power at very high rpm. A 650cc single-cylinder engine should work good with carburetors around 34mm to 40mm. A 42mm might work OK, but it would probably sacrifice a lot of low-end power for high rpm power. The stock carburetor is billed as a 40mm carb, but it’s venturi cross section is more on the order of 35.4mm. It’s a constant velocity (CV) carb, so it has a butterfly and throttle shaft in addition to the typical slide. It probably flows about the same as a 34mm variable venturi carb (Mikuni VM, Keihin PWK, DelOrto, Amal, etc.). One of the goals of this project is to build our hotrod on a tight budget. With that in mind, I had been searching the internet for a bargain basement carburetor. About nine months ago, I found a deal on Amazon that was just too good to pass up. It was a Keihin PWK40 for $28 bucks. I had no idea what to expect, but hey, $28 bucks???? I figured I could take the risk. With shipping and tax, the whole shebang came out to $36 dollars. https://www.amazon.com/PWK40-40mm-PWK-Carburetor-Carb/dp/B07M824BB2/ref=psdc_404758011_t1_B003CJEESK |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:24:35 Exactly one-month later this box was at my front door. Hmmmmm? Japanese carburetor, Chinese box. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:25:49 I’m not overly concerned about where it shipped from, or even where it’s manufactured. For this project, I just want a carb that is cheap and works well. So, I rip open the box and guess what, there was another box inside. Gosh, I didn’t know Keihin and Sudco are located in China. Somehow, I get the feeling that Keihin isn’t really involved with this carburetor, or Sudco either. Right away I noticed that the box identified the carb as both a PWK38 and a PWK40??? For $28 bucks, I could dig either one. Guess I’ll have to measure it. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:26:24 It says it’s “MADE IN JAPAN”. Who knows, maybe it is. Looks legit. Remember, $28 bucks. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:27:12 I opened the second box and was pleasantly surprised. It looked top notch. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:28:14 I had previously tried a PWK38 Air Striker on my high-compression hopped-up Savage. It worked great. That one was also of questionable pedigree. I figured I might get similar results with this standard PWK. We’re putting it on a stock engine, so it should provide enough air and fuel. Let’s take a tour of this mixmaster before we slap it on the motor. The airhorn & venturi are all polished up. It’s a nice big hole, but it ain’t 40mm. It’s 40 at the outlet, but at the mid-point it’s only 37.4mm. I flow tested it. It flowed the same as my first PWK38. So, it’s a 38. No biggie. Just keep thinkin $28 bucks. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:29:02 This thing is way lighter than the stock carb, and way lighter than the VM38 too. That’s a nice feature. It will reduce the stress on the rubber manifold. From the left side, you can see that it has the standard adjustment screws for idle speed and mixture. It’s also shorter than the stocker and the VM. That provides a little extra room for maintenance. It has a nice enricher knob that is easy to operate, and there’s a big drain plug that permits quick & dirty jet changes. There are four bowl vent connections. You won’t have any problem finding a convenient place to pipe up the vent tubing. Cap off the ones you don’t use. I’m not a fan of the forward-facing fuel nipple, but you get used to it. Lovin that official Keihin logo and the Sudco sticker. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:29:36 On the previous PWK Air Striker, I couldn’t figure out where the main air bleed was. I found it. You have to remove the idle mixture screw to see it. Unfortunately, it’s a fixed .075” air bleed. I have some ideas on how to deal with that. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:30:35 On the right side, you can see the other two bowl vents. The nipple on the bottom is the overflow. That’s a “love it or hate it” proposition. Either you love the idea of not flooding the airbox and crankcase when your float valve sticks, or you hate the idea of burning down the garage when your float valve sticks. Always turn your petcock OFF when you shut down your bike (even for just a few minutes). That spigot is smaller than the stock carb. It’s a bit loose in the stock manifold, but it works fine if you use the correct clamp. More on that later. Note that it’s for racing only. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:31:28 The slide is unusual, sort of a cross between a round slide and a flat slide. There are no markings on it. I have no idea what the slide cutaway is or how to measure it. Likewise, the needle has no markings. Careful measurement confirms that it is very close to a DGJ or a DGK. The throttle return spring looks whimpy, gotta pay attention to that. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:32:08 There is a little contraption that threads into the slide. You have to remove it to adjust the needle position. The throttle cable hooks into the contraption. There is a small nylon ring that locks the cable in place. One nice feature is the cable end is captured. If the swaged cable end comes off, it can’t run through your engine (always painful). |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:33:01 This shows the nylon lock ring on the end of the spring. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:33:37 The float bowl has a formed o-ring seal. Replacements are available on eBay and Jets-R-Us. The brass tube sticking up is the overflow. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:34:27 This shows the internal parts, float, needle & seat, jets, etc. Standard Keihin jets fit perfectly. There’s a baffle assembly built into the metering block. It keeps fuel from sloshing away from the main jet under hard acceleration, cornering, or breaking. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:35:03 The needle & seat flow 14.25 ounces per minute. To support 50 horsepower, you need about 8.5 ounces per minute. That 8.5-ounce flow requirement includes a cushion, so looks like the PWK will have enough fuel to get the job done. It has a decent size hole in the seat. The needle is typical of what you would expect in a Japanese carburetor, soft tip, spring-cushioned pin, float clip, etc. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:35:46 The metering block is held in place with tamper-proof torx screws. I could not find a part number for the metering block, but I was able to find the formed o-ring that seals the metering block to the carb body. The metering block houses a non-replaceable needle jet, so having the ability to remove the metering block might come in handy. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:37:18 You need a throttle cable to install the PWK. Lancer sells a cable for his VM carbs. As I recall, he sells several different cables for various model years. I have a 2016. His part number SP-005 worked good for me. If you have a different model year you might need a different part number. The Barnett cable does not have enough adjustment to allow wide open throttle (WOT). That’s easy to fix. There are two holes in the twist grip. One is for a cable to open the throttle, and the other is for a cable to close the throttle (push/pull setup). The Savage only uses the “open” cable. If you relocate the cable to the second hole, it takes up the excess slack and you can adjust the cable to achieve WOT. If you have a different throttle assembly, be creative. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:38:10 Extend the cable slot to the second hole. A hacksaw works good for this job. Be careful, don’t saw too deep. Maintain the same depth as the existing slot. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:39:03 Now the cable end can be installed in the second hole. Test it with the housing reassembled to make sure that it doesn’t bind or catch on anything. It must operate perfectly smooth. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:40:07 Another option is to modify the stock throttle cable. Fast650 has done that on his PWK38. He shared these pictures with me. He files down the cable elbow so that it will fit in the socket on the top of the carb. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:40:53 And he carefully files or grinds down the cable end so that it will fit in the slot in the PWK slide. Seems easy enough and should save a few bucks. Check-in with the Fastman for the gory details. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:41:49 You need a new airboot to attach the PWK to the stock airbox. I used a 2” rubber pipe coupling and made an adapter out of an ABS fitting. It all fit perfect; looked factory fresh. Before you install the boot, you have to make sure that the slide goes all the way open when you twist the throttle to the fully open position. Adjust as necessary to achieve WOT. I believe Fast650 overame the airboot issue by turning his stock airboot around. Again, check with the Fastman for specifics. It’s an easy mod. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:42:39 You can see there is ample access, and everything looks factory. As mentioned earlier, you need a special clamp for the intake manifold. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:43:27 This Ideal 5/16” wide #32 stainless steel worm clamp does the job. The stock clamp has limited range. The picture shows the Ideal #32 clamp on the top and the stock clamp on the bottom. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:44:03 The decompression relay needs to be relocated. Just zip tie it to the frame |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:48:14 I already had a good idea where the jetting should be. As delivered, this carb is way too rich. It had a #55 pilot jet and a #160 main jet. I changed the jets before I installed the carb (#40 pilot jet, #140 main jet, needle clip in center groove). The K&N flat panel filter was in the airbox (sans cover). Ready to rip. It started right up and ran good. Idle was a bit rich but overall, it felt good. After a bit of grooming, it was dialed in. Under normal cruising conditions it ran perfect. Easy to start, smooth idle, great throttle response, no surging, no hiccups, no afterfire (with the exception of a little cackle crackle on deceleration). Absolutely no KaBooms. Once I was sure it wasn’t too lean, I started doing timed pulls. It had this unnerving tendency to go rich at high rpm. Start pulling back on the main jet and things improved up top, but then it would be lean at initial WOT. No amount of fiddling could rectify the problem. It sure was looking like the flat-panel air filter was choking things off. It could flow enough air at the lower rpms but couldn’t keep up as the engine speed increased. The PWK couldn’t match the stock carb. That just didn’t seem right. Could the stock cylinder head be limiting flow? Possibly. But it looked more like the filter. Let’s look at the setup. Completely stock engine, airbox cover removed with K&N flat-panel filter element, stock exhaust header, LCGP high flow muffler. With the stock carburetor this setup ran: Second Gear 4K to 7K: 3.55 seconds Third Gear 4K to 6.5K: 6.53 seconds Fifth Gear 3.5K to 5K: 5.72 seconds Fifth Gear 3.5K to 5.5K: 9.19 seconds With the PWK carburetor this setup ran: Second Gear 4K to 7K: 3.66 seconds 0.11 seconds slower than stock carb Third Gear 4K to 6.5K: 6.64 seconds 0.11 seconds slower than stock carb Fifth Gear 3.5K to 5K: 7.01 seconds 1.29 seconds slower than stock carb Fifth Gear 3.5K to 5.5K: 10.26 seconds 1.07 seconds slower than stock carb |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:49:11 Time for a new filter setup. Prior to this project, I had been running a K&N cylindrical filter in a highly modified airbox. The K&N RD-0710 is 3.5” diameter by 5” long. It has over twice the area of the flat-panel filter. At $39 its cheaper than the flat-panel filter. It worked good with the souped-up engines. Let’s see how it runs on a stock engine. Will it fix the problem? It’s a simple setup. The K&N filter with a 2” ABS street elbow and a 2” rubber coupling. Here it is on a VM38 under test. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:49:57 You have to cut the top off the airbox. The arced portion in the front serves as a cradle to help support the filter and elbow. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:50:38 Cut an opening in the back of the airbox for clearance. The tubular foam insulation in the bottom of the airbox supports the weight of the filter and elbow. The zip tie over the front of the elbow secures the assembly to the airbox. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:51:23 Install a simple mudflap on the rear fender to help keep the dirt and water off the filter. There’s never any crud in my induction system, so I think the mudflap and filter are doing a good job. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:52:50 Although the airbox still has a nipple for the engine breather hose, there’s no way to attach a breather filter. A catch can assembly takes care of that. Here’s one installed on an S&S carb setup. You can use a similar catch can on the PWK installation. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:53:45 Once installed on the motorcycle, the cylindrical air filter looks professional (IMO). |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:54:28 All the factory components still bolt right up. The ignitor box and decorative tins still attach to the airbox, right where the factory intended. Now we’re talkin AIR FLOW. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:56:26 Right off the bat I could tell the difference. Now it would pull past 7000 in third gear (all the way to 7300). After a few test & tunes, it was time to see how it did against the stopwatch. I achieved best performance with a #35 pilot jet, #142 main jet, and the needle clip in the fourth groove (rich). Second Gear 4K to 7K: 3.24 seconds 0.42 seconds faster than flat-panel Third Gear 4K to 6.5K: 5.77 seconds 0.87 seconds faster than flat-panel Third Gear 4K to 7K: 8.85 seconds Fifth Gear 3.5K to 5K: 5.65 seconds 1.36 seconds faster than flat-panel Fifth Gear 3.5K to 5.5K: 8.70 seconds 1.56 seconds faster than flat-panel |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 01:58:55 Progress. Now it’s behaving like it should. It’s measurably faster than the stock carburetor (second gear -.31 seconds, third gear -.76 seconds, fifth gear -.49 seconds), and it pulls well past 7K in third gear. But…. would the stock carb have benefited from this new air filter setup? Time to switch carbs. It was a simple job to throw the stock carb back on, but tuning was another story. It couldn’t get enough fuel. Running the stock header, I had previously achieved best time with a 155 main jet and the special compound slide needle at +.08. Now it would hardly run with a 155 main jet. It was scary lean. It ran best with a #200 main jet. The bike felt good with that big jet and big air filter, but the stopwatch don’t lie. Even though it felt gangbusters, had great throttle response, perfect idle, zero afterfire, the whole enchilada, it was slower than it was with the flat-panel filter. We’re not talkin gross disparity, but it was measurably slower. After numerous WOT pulls and much fiddling around with jets & needles & clips & spacers, it was apparent that it wasn’t gonna get any faster. Something about that filter didn’t sit well with the stock carburetor. I suspect it has something to do with the differential pressure across the diaphragm, but I’ve got no way to test that. With the K&N RD-0710 filter the stock carb ran: Second Gear 4K to 7K: 3.53 seconds 0.02 seconds faster than flat-panel Third Gear 4K to 6.5K: 7.08 seconds 0.55 seconds slower than flat-panel Fifth Gear 3.5K to 5K: 5.68 seconds 0.04 seconds faster than flat-panel Fifth Gear 3.5K to 5.5K: 9.43 seconds 0.24 seconds slower than flat-panel |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 02:00:52 Time to reinstall the PWK and try it with the Mac header. That was a simple operation, no surprises. The bigger header along with the increased air flow worked great. Jetting remained the same. Pilot jet #35, main jet #142, slide needle clip fourth groove. The stock engine with K&N 3x5 cylindrical air filter, PWK carb, Mac exhaust header, and LCGP high flow muffler ran: Second Gear 4K to 7K: 3.13 seconds 0.11 seconds faster than stock header Third Gear 4K to 6.5K: 5.58 seconds 0.19 seconds faster than stock header Third Gear 4K to 7K: 8.20 seconds 0.65 seconds faster than stock header Fifth Gear 3.5K to 5K: 5.48 seconds 0.17 seconds faster than stock header Fifth Gear 3.5K to 5.5K: 8.29 seconds 0.41 seconds faster than stock header It maxed out at 6200 rpm in fifth gear (200-rpm increase). It pulled 7400 rpm in third gear (200-rpm increase). Based on the acceleration times, it’s obvious that the larger carburetor combined with the larger header improves overall performance. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 02:01:51 A carburetor installation wouldn’t be complete without a fuel economy test. She went 63.3 miles and gulped down 1.14 gallons of 89 octane E-10. It was an economy test, so I behaved myself. It got 55.5 mpg. Mileage decreased 9.5 mpg. That’s a significant decrease in fuel economy. I’m not sure what’s up with that. I did the mileage run with the stock header. I thought economy would be better with the small exhaust pipe. I guess I will have to try again. Maybe I can find a few more mpg with the Mac header. I’ll let ya know. Temperatures remain normal. Cruising on the freeway, oil temp is usually around 210°F and cylinder head temp (CHT) is usually around 310°F. When you start doing a lot of WOT runs, the CHT comes down a bit. The open induction system doesn’t affect noise much. Using my iPad with the NIOSH app, the noise levels at 1300/3000/4000 rpm are 66/78/79 dB. Looks like the wide open airbox is 2dB louder at idle and 1dB louder at 3K. It’s not any louder at 4K. That seems acceptable to me. It’s quiet. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 07/08/21 at 02:09:03 This completes the carburetor portion of the project. All it took was a little more air filter to get the budget mixer up to speed. I think $28 bucks for the carburetor was $28 bucks well spent. The jetting is dialed in. That budget carb is so sweet I ordered a 36mm to play around with. I’m curious how the two stack up. These carbs might be an excellent solution for the folks who have a mixer that just spent the last two years with fuel in the tank and the petcock left on. One of those beauties that look like the LaBrea Tar Pits. Let’s take a look at the results using test data from the stock header setup (keeping the project simple & cheap). The setup includes a completely stock engine, PWK38 carb, K&N RD-0710 air filter, modified airbox, catch can, stock exhaust header, LCGP 2.5” resonator with baffle. We have improved the overall performance of the motorcycle. Carburetion is excellent but fuel economy is down by 9.5 mpg. Backfiring has been eliminated. Audible noise has increased a modest amount, but the quality of the exhaust note is more pleasing to the ear. Compared to the box-stock motorcycle, third gear acceleration has improved by 4.71 seconds, and fifth gear passing acceleration has improved by 3.82 seconds (13.73 seconds if you run it all the way up to 5500 rpm). I think that’s pretty good for such a small investment in time and money. We haven’t done any major work; the engine hasn’t been opened up. Most of us could accomplish these simple modifications for under $350 bucks. The tests show that if you throw on a bigger header it will be a bit faster with no appreciable loss of grunt. All the easy stuff is done. We have picked all the low hanging fruit and kept a close eye on our bank account. Now it’s time to start doing some open-heart surgery. As I recall, the general consensus was camshaft next. Part 5 will install a DR650 cam. At this point, I have done 153 WOT acceleration pulls to dial in the different combinations. There’s a little over 2000 miles on the engine since it was restored to box-stock configuration. The old girl is holdin up good. No leaks. No ugly noises. Not using any oil. Zero oil accumulating in the airbox or catch-can. It’s a solid motor. I hope some of you find this project informative and can use the data I collect to help make decisions on your own project. If you have suggestions or comments on my test methods, post a reply so we can discuss. As mentioned earlier, if you have a particular component or modification that you would like to see included, let me know and we can collaborate. Best regards, Mike |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Armen on 07/08/21 at 07:04:09 Thanks for all your hard work and careful documentation! The Chinese counterfeit stuff is crazy. Supposedly there are fake NGK spark plugs out there that fall apart. Funny, because when I was growing up the Japanese were doing crap copies of Western stuff, now it's their turn to get bit on the ass. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 09/13/21 at 15:49:10 I wanted to alert everyone about a problem I had with the 2" ABS elbow used to connect the air filter to the carb boot. I've been testing a new engine and went to make an adjustment on the carb. While removing the air filter I noticed a big crack in the ABS elbow. The elbow was essentially crumbling in my hand. This elbow is not under any stress, and it doesn't get hot. I've been running it for a long time (since about December of 2019). I guess the fuel vapors eventually break down the ABS plastic. I picked up an ABS replacement just to keep my test program going and ordered a PVC 2" street elbow. I have a sample PVC fitting soaking in gasoline to see how the PVC holds up. Anyone else have any trouble with ABS? Anyone else tried PVC? |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Jdvt600 on 09/13/21 at 16:47:11 I have a PVC pipe between my air intake and filter. I installed it mid June and there are no visible signs of deterioration. I heated the PVC with a heat gun to shape it to mate with the Uni air filter. I'll keep visually and physically inspecting it going forward. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Gary_in_NJ on 09/13/21 at 17:24:55 If a piece of the PVC made it past the Venturi, it would be a bad day |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Eegore on 09/14/21 at 05:48:57 If it is not high-density polyethylene (HDPE) it should decay from gas vapors. The rate of decay depends on too many variables to break down just for this application. ABS I would expect to decay over time, but how much time depends on a lot of things. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 09/14/21 at 10:58:25 Absolutely correct Gary. A chunk of that ABS through the carb and it would have been a bad day. Fortunately, all the pieces stayed in the elbow. It fell apart when I went to remove it. The PVC test specimen is still in the gas. I haven't pulled it out but it looks OK. Eegore, do you think PVC (white) will hold up better than the ABS? Jdvt, thanks for the input. Please let us know how your pipe holds up. One thing I noticed on my elbow was a slight oily residue in the area where it failed. I had been seeing that residue for several months but there was no crack that I know of. It just seemed to all-of-a-sudden fail. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Eegore on 09/14/21 at 11:48:53 "Eegore, do you think PVC (white) will hold up better than the ABS?" Type 1 schedule 40 PVC if that is what you are testing should be stronger than ABS in this application. Type II would have higher thermal ratings and rigidity. My understanding of PVC is that the chemical process never really stops which is why new PVC is very strong and old PVC shatters like glass. Standard PVC is typically rated for cold applications, like water, and will deteriorate faster in the sun even with UV protections. If it were me I'd use chlorinated PVC. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by badwolf on 09/14/21 at 12:30:17 Just my $.02, rv's use a black form of plastic pipe. (I used some years ago making darkroom equipment. It held up very well with the chemicels involved. ) You would have to go to a rv dealer to get it. Something else to try. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/08/21 at 17:27:56 Thanks for the suggestions Eegore & Badwolf. I ended up using a white PVC elbow. Not sure how I could tell if the PVC is chlorinated. It's amazing how bad the ABS elbow was. I picked it up off the bench the other day and it pretty much just fell apart. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/08/21 at 17:30:11 As I previously mentioned, I did a fuel soak test of a PVC coupling. It sat in the jar a little over one-week I believe. It didn't get soft. Measured it with a dial caliper and it was stabile dimensionally. It didn't discolor. Figured PVC was good to go. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/08/21 at 17:32:11 Used a NIBCO J4807-2. Again, it needs to be a street elbow. Didn't have locally. Ordered on eBay. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/08/21 at 17:33:22 A quick coat of paint made it look factory. Glad I caught this when I did. Would have been an ugly failure. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Dan Stafford on 11/12/21 at 23:14:31 Hey Mr Mike! My PWK is on the way! Just had a couple ?s about the “catch can” run a breather filter? My broke self will probably be modifying the stock cable. So i guess i need to order a jet kit also? Thanks for your help Dan |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 11/14/21 at 15:45:24 Yes, you need to run a filter. You should also buy a selection of jets, probably #135 through #145 main jets, and a #35 through #40 pilot jets. The generic Keihin PWK replacements that Jets-R-Us sells work just fine and cost about half what the genuine Keihin parts cost. Don't forget the special stainless steel Ideal clamp for the carb manifold. This post gives some details on the catch can I use. It's cheap and easy to construct. Some folks (like Serowbot) just install a small breather filter on the end of the breather hose. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1570415428 What are your plans for the air filter? Good luck, Mike |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Dan Stafford on 11/14/21 at 16:15:24 Mike, Probably go a similar route such as you did. However I’ll probably just use a rubber boot that shaped 90° for plumbing. Same air filter. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Dan Stafford on 12/01/21 at 22:25:13 BOOM! |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Dan Stafford on 12/04/21 at 16:51:01 On the cable portion did you cut the elbow out and length in the cable because I only have about 3 inches coming out of the top of the carburetor to try to hook all of that up and it’s impossible |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Dan Stafford on 12/04/21 at 16:52:37 Or I’m probably being a complete bonehead by leaving the throttle at the top on the handlebars connected when I should loosen that that way I’ll have cable slack lol |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Fast 650 on 12/08/21 at 11:27:10 Are you using one of Lancer's cables or did you modify the stock cable? If it is a modified stock cable, the housing is about 5/16 to 3/8 of an inch too long. You will need to shorten the housing by that amount or the throttle will not close completely. It is easy, let me know if you need a how to on that. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Dan Stafford on 12/08/21 at 11:36:42 I modified mine, I got it working well, working is a bold statement. It runs it falls on its face at low RPMs. My jets are in the mail however all this Amazon crap is got them delayed till tomorrow or something, which is OK because I’m on a work trip in Alabama currently. Working my way to Tampa and then hopefully they’re in my mailbox when I get home or my wife didn’t lose them lol, same with my Canaan air filter is in the same shipment as the Jets. I just feel like the throttle cable could be smoother. I did as you recommended and use the hacksaw to open up the plastic piece on my throttle lever, it may be the spring in the slide that I’m feeling. I hate being away from my motorcycle >:( |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Dan Stafford on 12/08/21 at 11:44:00 These are both Charlotte pieces of pipe however, also they are both Street 90s but one is a long pool sweep 90. It’s about a half inch longer than the regular one. I’m just gonna hang onto them both and perform fitment when my filter gets here or there, I got creative with some electrical tape in my hotel room last night for the blue one yeah I was bored. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Yazman on 09/19/22 at 17:51:16 DragBikeMike, Any updates on the PWK38? I have a $40 Amazon credit burning a hole in my pocket, and I'm planning on getting the cheap knockoff and modifying my stock throttle cable to work with it. Are you still happy with it? |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 09/19/22 at 18:29:40 Yes, pleased as punch. I've probably got somewhere north of 15K miles on it. It never needs attention. Always runs perfect. Never needs adjustment. It's been totally reliable. I'm anxiously waiting for Sneezy to get his runnin. He got his from a different vendor and there were some kinks to iron out. I got two from JFG Racing, a 40mm (actually 38) and a 36mm. They both were good quality and worked great. I only ran the 36mm briefly. It robbed too much from my top end. The 38mm runs much better all-around and has a killer top end. The 36 runs great up to about 5.5K and then signs off. I much prefer the 38. It doesn't give away any bottom end and extends the top end a good 1500 rpm or more. Like all things "knock-off", it's a crap shoot. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Yazman on 09/19/22 at 19:23:50 63656A16141317270 wrote:
Nice! So all I need for the complete set up is: 1. Knockoff PWK38 2. Pod filter (already have) 3. Modify stock throttle cable (cutting and sanding?) 4. Narrower hose clamp possibly 5. Extra jets (which kind?) Am I missing anything? |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by TheSneeze on 09/20/22 at 13:24:06 I went and bought another from JFG Racing. Much better quality, and I will be putting that one on my hot rod motor. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 09/22/22 at 02:41:51 Yazman, I suggest you wait until you have the carb in hand before ordering any jets, needles, etc. Theduderino received one with a different needle jet configuration that would not permit installation of standard Keihin main jets. It needed shorter jets. Your main jet should look exactly like this. If it doesn't, you may have the removable needle jet setup. Not necessarily a bad thing. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 09/22/22 at 02:44:33 Theduderino's looked like this. There was a removable needle jet and the main jet threaded into the needle jet. He had a bit of difficulty ironing out his main jets. There's a lengthy post on here that goes over all the details. Theduderino may be able to elaborate. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 09/22/22 at 02:45:55 You also should verify that the slide cutaway is a #7. Here you see the various slide cutaways. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 09/22/22 at 02:46:30 Here are the slide cutaway dimensions. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 09/22/22 at 02:50:14 Here's how to check the cutaway to verify that it's a #7. Just place the slide on a flat surface and verify that a letter "W" drill bit just starts into the cutaway. The letter "W" drill is .386", close enough. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 09/22/22 at 02:53:12 Hey Sneezy, did you ever open up the JFG carb and check things out? Does it have a standard PWK main and needle jet setup, or does it have that removeable contraption like Duderino's? Is the slide a #7? |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by TheSneeze on 09/22/22 at 07:29:28 No, I have not opened it up yet, but with all this talk going on I think I will finally crack that egg and see how nice the yolk looks. ;) |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 10/02/22 at 11:46:20 Great work Mike!! I love your approach and attention to detail! Thanks. I am also trying this approach on a non-running bike that I got cheap and don't want to sink a bunch of money in it until I know better what I bought. It had no carb so I bought the PWK40 at JFG Racing. It came with a #170 and #50 jet installed (I think they are standard Keihin size, but I'm not an expert on jets). The e-clip was installed in the 4th slot which I found interesting (usually in the middle slot). They also included an extra 45, 55, and 165 and 175. Sorry, I got a little confused in your jetting with different air filtration and exhaust scenarios (I'm old and easily confused). My bike has a stock exhaust and flat panel air filter in stock air box. For jetting purposes, I'm thinking #35 and #140 and start with the e-clip in the 4th slot. What do you think? Thanks in advance!! PS - For the stock throttle cable modification, I just snipped and filed down the bullet bead to what you say is a size 7. I just kept test fitting it into the slide and through the carb top (you'll know when you get it right - takes some patience to get round and smooth - which isn't my strong suit). In order to get enough exposed cable, I just hack sawed off the end nipple of the elbow on the carb end and filed it smooth. It fits like a glove in the top of the carb (firm but still swivels). That's hacking off a bit more than needed, but it was a clean location, and it's still in adjustment range at the throttle cable adjuster to remove free play. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Yazman on 10/02/22 at 16:46:08 Thanks DBM! And thanks ThumperPaul for the cable tip. I got my PWK38 from JFG today, and it has 170 and 50 jets on it too. I ground down my cable barrel with a Dremel until it fit inside the top slide thing. I cut off the tube where it gets narrower as Paul did. The metal end of the throttle cable isn't secured to the top of the carb, so it kind of moves around when I work the throttle grip. I'm thinking about maybe electrical tape and then epoxy on top? I'm not sure how the jetting will work with a pod filter and fairly open exhaust. I'm only going to run for another week before I tear it down and throw in the high compression piston and cam, so I guess I'll have to monkey with the jetting anyways. I don't really understand where the clip is or how to get to it. But I assume it is set up like Paul's. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Yazman on 10/02/22 at 17:13:59 It fired up! That was easy, and $36 well spent. I spent less than an hour total, including modifying the stock cable. The only problem: If you look in the pic, you can see that the throttle cable tube sticks up way high. I'm not sure how to get around this. And ideas? EDIT: Also, what's with the octopus/spaghetti tube deal? Are these all just puke tubes? It seems awfully excessive... |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 10/03/22 at 04:57:22 Hey Yazman. The 10’ of vacuum tubing seems like you are unpacking an octopus! Lol. The 2 tubes (1 located on each side) are “extra” for some other kind of bike that wants/needs this BS. If you try to blow or suck through those tubes, you get nothing - they are blocked off. If some bike needs them, they would have to be drilled out to function. The 2 tubes on top of the carb are breather tubes. Like the stock CV carb, just stuff those under the gas tank (I’ll probably shorten them a bit - too much tube dangling around.) I haven’t installed mine yet - waiting for jets to arrive tomorrow. But I am also concerned about the height of the carb where the cable throttle elbow goes. Hopefully it will have clearance with the gas tank put into place. I would not put epoxy on the top of the carb where the cable inserts. Mine sits in there pretty snug and swivels. Swiveling is actually good/okay. Using the cable free play adjuster, I’m able to get mine to sit down in the inlet of the carb sufficient. May have to come back to this, but I’m leaving as-is for now. Unless DragBikeMike has a different recommendation, I’m going with a 35 and 140 jet. I’m at sea level in Houston. The set of jets I bought also includes a 38 and 145. Those might get a try too. Keep us posted. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Yazman on 10/03/22 at 17:06:03 WOW! I popped on the carb as it came out of the box (50 &170 jets), and this carb is AMAZING. My old carb was good at 65+ degrees, poor at 60 or below degrees (full choke for 20+ minutes and still not running right ), but this carb blows the old one right outta the water. I didn't need any choke, ready to ride immediately, significantly more torque and acceleration (butt dyno, but for real). I'm incredibly pleased for $36. My throttle cable is still all just flopping around. The metal tube doesn't even touch the top of the carb, so there's like a quarter inch where it's just the braided cable exposed. It works for now ok though. Thanks ThumperPaul for bringing me up to speed with all those tubes. I was nervous thinking about where they all hook up lol. Is anyone surprised the 170 & 50 jets worked so well? Feels like everyone uses way smaller jets Here's the details: Bike: 2011 RYCA Mods: pod filter, flow through exhaust, PWK38 Temp: 60F Rider: 150lbs Gas: 87 octane Miles: about 10k |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:27:43 Yes, I am amazed that those giant jets worked well. I will address your prior questions first. I caution you about the GIANT jets. If it runs good with a #170/#55 combo, something is probably not right. Yazman, the four tubes on the side and top of the carb are bowl vents. These carbs are intended for 2-stroke dirt bikes (probably 400 – 500cc). As such, they have a quad-vent system to keep the engine from flooding as the beast bounces along over big ruts and jumps. It also helps when you fall down, keeps the engine from flooding while you pick up the bike. As ThumperPaul says, you can plug the two on the side, like this. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:28:20 And the two on top can be routed up into your frame backbone just like the stock carb. Again, just like ThumperPaul says. It should look like this. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:30:08 The tube off the bottom of your float bowl is an overflow. It should be routed straight down like this. Make sure it exits below the engine and away from the exhaust. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:30:49 I would not epoxy your cable. Just let it swivel. If you epoxy the cable, you won’t be able to screw the top of the carb on & off. I run a Barnett cable and it runs below the frame tube, like this. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:31:20 The cable runs under the frame backbone and to the right side, similar to the stock cable routing. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:31:52 Then it runs under the decomp solenoid und up through the forks just below the headlight. Again. Same as the stock cable run. I use a small adel clamp to support the cable and keep it off the head cover. The clamp doesn’t grip the cable. The cable is free to slide in & out of the clamp. The clamp just supports the cable. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:32:40 You might wanna PM Fast650 to see how he routed his stock cable and see how he dealt with the elbow issue. Regarding the “clip”. What clip are you talking about? If it’s the “e-clip” that ThumperPaul mentions, that would be this. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:33:28 Note that there are five grooves in the slide needle. Those grooves along with the e-clip provide fine adjustment for your mid-range mixture. Placing the e-clip in the top groove will provide the leanest cruising mixture. Placing the clip in the bottom groove will provide the richest cruising mixture. The middle groove is a good place to start. The e-clip is captured under the contraption that your throttle cable hooks into. This shows the assembly with the e-clip in the richest position. The special cable hook contraption is threaded into the slide. Once installed, the e-clip and slide needle are captured. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:34:17 The special white nylon collar locks the cable into the hook contraption so that it can’t come out. Don’t forget that nylon collar. It’s a real juggling act getting all this stuff together. Be careful, you don’t want the throttle to hang open. Test it thoroughly to make absolutely sure that it ALWAYS closes completely when the twist grip is released. This shows how the white nylon collar gets assembled. Unfortunately, you have to install the hook contraption into the slide before you install the cable, spring and collar. Its significantly more difficult that this photo implies. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:35:16 As you can see, all the stuff is deep down inside the slide. Hard to work in there. There’s a little tab in the white nylon collar that has to go in the cable slot. As I mentioned, a real juggling act. Again, be careful, test it thoroughly, make sure the slide returns to the closed position. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:36:44 I wouldn’t try to ride it very far with those jets. A #170 main and a #55 pilot are gonna foul your plug in short order. Get a proper set of jets in there. Probably best to have a #135, #138, #140, #142 & #145 on hand for tuning the main circuit. A #35 pilot jet should be fine (probably just a tad rich but it’s the smallest available). Can you post some pics of the interior of your carb so we can all see what’s in there? I want to make sure you don’t have a main jet setup like Theduderino has. Yes ThumperPaul, the #140 main, #35 pilot, and clip in the 4th groove from top are good for starters. The clip can go in the 3rd or 4th groove. Just keep an eye out for lean surge at cruise. If you got any of that goin on, just raise the needle one-groove. BTW, I have found the generic jets offered by Jets-R-Us to be just fine. They are good quality and half the price. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:43:52 Regarding your condition where the engine runs great with a #170/#55 jet combo, if it runs great with those jets there’s a good chance you have a whopper of an air leak, or some sort of other crazy situation. Be careful with it. It should fall flat on its face when you go WOT. Try testing it with the main jet removed (don’t lose the brass washer above main jet). Make sure it runs crappy at WOT. If it still runs good with the main jet removed, you might have a needle and/or needle jet that control flow at WOT. That’s no good. The main jet must control fuel flow at WOT. Pictures please. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/03/22 at 17:48:54 Yazman wrote: "My throttle cable is still all just flopping around. The metal tube doesn't even touch the top of the carb, so there's like a quarter inch where it's just the braided cable exposed. It works for now ok though." DANGER. Must fix. :o |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Yazman on 10/03/22 at 17:56:56 Thanks for the detailed info! I'll have to wait until I get another hour of free time to open up that carb again (kids, work, etc). I have some pictures of the jets though. First jet: |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by Yazman on 10/03/22 at 17:58:41 Yeah, I'm as dumb as I look. I will have to fix that cable first thing! I can't really think of a way to keep it attached to the carb top though. Second jet: |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 10/04/22 at 05:10:28 Mike, you are awesome! I’ll take a few pics later today and share. Really appreciate the additional info on the #35 jet. I was thinking it might be too lean given it’s the smallest jet available. I’ll go with it and the clip in the 4th slot. My jets are scheduled to arrive today (I got a kit of 40 pieces for $14.99 - what could possibly go wrong, lol. 10 of those jets aren’t compatible, so 30 jets.) Yazman - double check and make sure the bead on the throttle cable is fully inserted into the contraption holding it in the slide. It should be seated all the way down that contraption. Make sure the nylon retainer is seated all the way down with the notch in the groove. I had to use a small screwdriver to persuade the bead into its slot and persuade the nylon retainer completely in. I’m not getting 1/4 inch of free play in the exposed cable length and we did the same hack. Are you adjusted completely out on the throttle cable adjuster on the throttle end of the cable? I’ll look at mine again and send a few pics. If the throttle cable adjuster is all the way in, there is plenty of thread to back off and thighten/remove the 1/4” free play. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 10/04/22 at 06:56:56 I used a couple of small zip ties on the dust boot to help secure it. It really shouldn't be necessary if the cable is adjusted correctly and the cable housing is completely trapped. The dust boot fits very snug on the elbow. Don't use any lubricant, just wiggle and fight it into position. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 10/04/22 at 07:00:23 With the cable adjuster all the way in at the throttle, this is how much exposed cable I have and you can see it relative to the spring length. The spring is right at 3" long in resting position and the exposed cable is about 2.75". |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 10/04/22 at 07:08:41 This is the slide wide open. To get the slide to open completely (WOT), I adjusted the cable by about 1/3" at the adjuster. You'll know when is right, when the slide bottom is flush with the top throat. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 10/04/22 at 07:36:05 Here's a pic of the throttle cable adjuster and the amount of adjustment I needed to get the slide to fully open. Yours may be a little different depending on how much your cable may already be stretched. My bike has about 14k miles and the cable has very little stretch if any. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 10/08/22 at 06:46:49 I wanted to share an update on my PWK40 installation. Below are some pics of the 'final' installation. I need to make a final adjustment on the offset length of the carb air boot that connects to the air box. If you look at the stock air boot, you'll notice it's slightly curved (banana bend) with the top and bottom being slightly different length. For this modified boot, I bought an 8" long 2.5" ID silicon hose - it needs to be cut to about 5.25" on one side and maybe 5.5" on the other side - this is the little tweak I need to make (measure twice, cut once - I should have done this instead of straight cutting it). The 2.5" ID is about perfect on the air box side and carb side. A pair of 3" max diameter worm gear clamps were used Note: these are 1/2" wide and work fine on this air box side of the carb. On the spigot size of the carb, I would strongly recommend staying with the 5/16" wide clamp that fits in the grooves of the spigot intake - this connection is critical to get the connection air tight. I need to hunt down a 5/16" wide worm gear clamp with a 1.75"-2.00" diameter fit (hard to find without paying a small fortune, the 1/2" are readily available in the plumbing dept of any hardware store). Silicon Hose: https://www.ebay.com/itm/393811095125 A couple notes/tips. It's running very good with #35 primary and #140 main jets with the e-clip in the 4th slot. I am 2.25 turns out on the air/fuel mix screw. It's a crispy lean at 2.0 turns out and the rpms drop a tiny bit at 2.5 turns out and the throttle loses some crispness. At Houston sea level and temps finally starting to come down, I'll be revisiting this over the coming months. Note: At 3 turns out on the air fuel mix screw, it starts to weep a tiny bit of gas at the screw. This seems to be a design weakness in my opinion, but I'd still buy this carb again (carb is very good for the price). Knowing this tells me to go up to the next primary jet size. We'll see what cooler weather does - I may go to a #38 primary and move the e-clip up to the 3rd slot and maybe I'll be around 1.0 turns out on the air/fuel mix screw. Photos below. Overall extremely pleased with this aftermarket carb modification. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 10/08/22 at 11:55:23 Thanks for the update Paul. Sure would like to see those photos you mentioned. Glad to hear that it runs good. After riding it for a while let us know how it's goin. You have probably seen Sneezy's latest post on his two PWKs. Can you tell us if you ordered a 38mm PWK or a 40mm PWK? Your's does not appear to have the removable needle jet. The fixed needle jet (like yours) is a standard configuration that utilizes the long Keihin main jet. Sneezy's has the removeable needle jet that requires a special short main jet (like Duderino's). I believe those were billed as 40mm. Would be good to know if the removeable needle jet is something unique to the 40mm or if it's a crap shoot. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 10/08/22 at 15:18:53 Thanks. I’ve been in contact with TheSneeze and he’s been extremely helpful like you. I came up with this concept idea well after you did and major kudos to you! The needle jet is removable, but it’s a bit funky - at fully tightened it still has 2-3 screw turns left. I thought it was wrong, but left it alone. It is weird though. I need to take a good ride, but garage testing is giving me good vibes. I’ll update more later. Hopefully you can see my pics now. I had to take a break and help my daughter with some plumbing issues. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/11/23 at 07:33:18 Hey Mike. Thanks for redirecting me back to this post! I couldn't find it to save my life yesterday. I've bookmarked it now! Ok, so now I've read back through this thread and I was happy at #35 and #140. Humm... So....what did I do that got me to #48 and #162...? I installed the Jardine muffler. Ahhh, the fun started... This seems like a huge jump in jet sizes for the muffler! Something else is up... I'm going to try a new intake manifold. I think I see a small crack. It doesn't seem to leak or be significant, but I want to try this with a new worm gear that I can clamp tight as hell. When I installed the carb, I did buy a new stock clamp, but I'm not 100% confident it's fully clamping with it's limited range. It's going to be over 100 degrees in Houston this week, so I'll dig into this rather than ride. I'll take some pictures this time too. This manifold has the part number you noted, but the ad says 42mm. I'm thinking that's an ad mistake and it's really a 45mm flange. Dare me to try it? lol https://www.ebay.com/itm/314611834710?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=314611834710&targetid=1645685073568&device=c&mktype=pla&googleloc=9027746&poi=&campaignid=20133407470&mkgroupid=147476396765&rlsatarget=pla-1645685073568&abcId=9312979&merchantid=6369394&gclid=CjwKCAjw4ZWkBhA4EiwAVJXwqcF6hA_ydddrZWLNlUwno87M05dAP9wyFoc7joaU_xUz5QFf196QQhoC9_UQAvD_BwE |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 06/11/23 at 19:19:00 "When I installed the carb, I did buy a new stock clamp, but I'm not 100% confident it's fully clamping with it's limited range." Paul, I'm 100% confident that the stock clamp won't work correctly. I would definitely change it with the Ideal clamp that has more range. I think the part number is specified herein. The Mikuni manifold link you posted looks to be correct. The PWK fits very tight in that particular manifold. I actually prefer the stock manifold. I make special adapters to tighten up the fit and then I epoxy them on the carb. But the carb works fine on the stock manifold without the adapters as long as you use a clamp with more range. Regarding your fuel mileage, I neglected to ask what size rear tire you are running, and what front pulley you are running. Can you fill me in on those items? |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/12/23 at 06:54:28 Thanks Mike. I wanted to install the Ideal 5/16" wide worm gear clamp, but I couldn't find one anywhere in the right diameter (like 2.5" or 50-60mm). Or I was going to have to wait like a month to get it and pay more for shipping than the clamp. So I bought a stock clamp. I'm guessing I may have gotten 1-2 good uses out of the stock clamp and now the thing won't clamp tight enough after being worked a few times and the bike has been bumped up and down the road and vibrated looser. I can confirm that the connection is not as snug as I'd like it (I know this issue well from tinkering on little dirt bikes. I should have suspected this earlier, but I think I get too anxious to get 'er back together and running to worry about it.). Why do you prefer the stock manifold? I really don't want to get into adapters and epoxy. If the Mikuni is nice and snug, why don't you prefer it? I went ahead and ordered the manifold from a different seller with a better description and it comes with a 5/16" worm gear clamp (probably really 8mm if from Japan or China). I'm inclined to use the new manifold and clamp instead of just hijacking the clamp and putting it on the existing stock manifold - but/so why do you prefer the stock manifold? My idea for an adapter/gasket to fill the tiny gap at the carb/intake is to wrap electrical tape 2-3 rounds until it shoves in there tight! :o The stock manifold seems to be made of very hard/firm rubber/plastic (not very pliable or flexible or responsive to a clamp) where the Mikuni appears to be made of more flexible softer rubber that would respond better to torqued up worm gear clamp. For the rear wheel/tire, I'm on a 140/90-15 Dunlop D404 (I guess you could pick up a couple mpg with a 130/90.). I don't think the front pulley has been swapped out and I don't think the gear box has been tinkered with, but I can't confirm for certain. I bought this bike for parts, but once I got it running with a new carb I decided to keep the bike. I don't have any real history - just hunches. Waiting for the manifold to arrive later this week. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 06/13/23 at 18:33:28 Paul, I prefer the stock manifold because it is robust, and it incorporates an o-ring. The stock manifold flange is very rigid. I have had trouble with the Mikuni manifold for the VM carb. It's soft and it bends. It eventually gets to the point where you can insert a feeler gage plumb through the flange joint. This is an example. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 06/13/23 at 18:35:26 For both the VM and the PWK, I make a thin adapter sleeve that I slip over the spigot and epoxy in place. This is an adapter for the VM. It yields a perfect fit in the stock manifold. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 06/13/23 at 18:37:02 This is an adapter epoxied onto a 36PWK. Very simple, works great, never had a problem with one. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 06/13/23 at 18:55:59 But as I previously mentioned, I have run the PWK in a stock manifold and it worked fine. Just need a clamp with more range. I'm also pretty sure the HS42 manifold you ordered will work fine too. It's a lot beefier than a VM manifold. I asked about your tire and gearing because they affect your odometer reading. Since the lion's share of my testing was done with stock gearing and a stock rear tire, the mileage numbers I was posting are "Savage Miles". If you put on a larger rear tire or a 25 tooth pulley or both, you are not registering the correct mileage on your ODO. If you just have a 140/90 Dunlop 404, you should correct your ODO reading by 1.046 before you calculate fuel mileage. For instance, if your ODO indicates you went 100 miles you actually went 104.6 Savage Miles. If you are running the 140/90 Dunlop 404 with a 25 tooth front pulley, you should correct your ODO reading by 1.138 before you calculate fuel mileage. So if your ODO indicates you went 100 miles you actually went 113.8 Savage Miles. If you are running a 140/80 IRC tire with the 25 tooth pulley, the correction factor is 1.092. Correcting the ODO reading will improve your mileage numbers a bit, but at your current 40 mpg the refined calculation will still be too low. Your fuel mileage seems way too low. Perhaps when you get the manifold and jetting squared away the fuel economy will be there. I've got a big motor with an inefficient pop-top piston and I never see anything less than 56 mpg. It's almost always in the low 60s. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/14/23 at 06:30:26 Thanks Mike. I’m going to make the manifold decision when I get the Mikuni and I can compare them side by side. The stock manifold bore size isn’t terrible off with the PWK40, but it could be tighter. I’ll probably just try the clamp first. Very interesting on the odometer reading low with the 140/90-15. And you’re right, even if I adjust I’m still only at 41-42mpg. I’d be happy with 50mpg. Parts coming this weekend. Thanks again, Mike. Oh, and how does "Drag Bike Mike" ever get 60mpg!!?? Downhill both ways? Lol. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 08:32:46 Hi Mike. I'm going to send a series of photos. I'm waiting on jets, manifold, and clamp - so I wanted to get these out for observation and diagnosis in case there is something else weird before I start tinkering. First photo shows evidence of air/fuel bypass at the clamp area. I have 2 more photos of the other sides and they show about the same amount of bypass. I have a strong suspicion this is why I have to 'jet up' so big to get the right air/fuel mix and poor MPG. I think I'll just try the new clamp without the new manifold. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 08:34:47 Air Horn view. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 08:37:43 Inside diameter of air horn side as best as I can manage holding the carb, camera, and meter. OD measures about 63mm which matches the product description in the ad when I purchase. The air horn is about 6mm wider ID and OD than stock. I fabricated a piece of 2.5" ID (almost exactly 63mm) automotive turbo tube to connect the carb to the box. It fits great at the air filter box and the carb with good tight clamps. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 08:49:50 I'm getting 39.8mm ID, but I call that user error/challenges holding everything for a photo. We'll call it a true 40mm. Note: the bore through the slide body and into air horn stays consistent at 40mm. I couldn't get a tool in there but I was able to feel it being flush at the intersection with my finger and small straight edge razor. It's a good 40mm through and through with no tapering down to 37-38mm. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 09:02:01 The jets and float and other good stuff... It has a removable needle jet and normal Keihin main jets work. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 10:10:41 A view of the removable needle jet and main jet removed. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 12:06:35 A pic of the slide, spring, and cable contraption. I'm not taking this monkey off the bike or apart if I don't have to!! What a bugger to get it together right (F-BOMB city)! |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 12:21:23 Intake manifold is in good condition. I think I'm going to whittle off those little retainer/alignment ears used with the stock carb. PWK40 doesn't need them and they want to come into contact with the carb body near the choke plunger. I want to make sure I get the carb as far into the intake as possible and 100% square as possible. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 12:55:21 New Mikuni 42 manifold just arrived. It is very robust. Nice quality. I buy from NicheCycle when I can. Usually very good quality and I’ve had great results on little Chinese dirt bikes with their stuff. I'm going to just hijack the worm gear clamp for now. As you noted, the stock manifold has an o-ring and I really don’t want to break the seal at the head (it looks good the way it is). |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 13:19:38 Oh man! I just did a test fit with the new Mikuni manifold. It is exceptional! I think I’m going to have to go with it! Slap a little high temp permatex on it! |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/15/23 at 14:16:24 Ms Bones. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 06/16/23 at 01:56:51 Wow Paul, thanks for all the pics. Especially the shot of the removable needle jet. Looks like they are on the 3rd iteration. I'm very curious how this carb works with those emulsion holes in the needle jet. Generally, placement of those holes is used to flatten out the fuel curve under WOT conditions. Holes at top affect lower rpm while holes at the bottom affect higher rpm. Pretty cool. I also like the fact that this latest iteration utilizes a standard PWK main jet, unlike Duderino's. I'm sure you will like that Mikuni manifold. Doubt that you need any sealant. And yes, that sucker fits tight. Your stock cable installation looks ace too. Thanks again for the pics. Can't wait to hear how it runs. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/16/23 at 05:26:15 Thanks Mike. Interesting info on the needle jet. I had no clue. Flattening the curve…. That’s pretty cool old school! How about richer at higher rpm’s when you wann stay cooler and leaner at low rpm’s? The mounting holes on the Mikuni manifold are larger and oval and not round. I’m going to get some larger washers and change out the screws for hex heads. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/16/23 at 09:17:14 Mikuni manifold installed. Shiny stainless steel 8.8 grade hex heads. I’ve torqued to about 12 ft/lbs. It feels and looks about right, but I want to verify torque spec if I can find it. Generic internet info suggests about 11.8 ft/lbs for an M6 bolt/screw. My manual is totally silent about the intake manifold. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/17/23 at 14:17:50 Mike, I went back through your photos. I did the same thing with my cable routing with my modified stock cable. Under the frame, like you said, like stock routing but I just did a poor man idea with a zip tie loosely attached to the frame. No issues and keeps the cable off the head without binding the cable. |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/18/23 at 11:32:10 162A372F3227301223372E420 wrote:
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by DragBikeMike on 06/18/23 at 23:21:11 "Adjusted the air/fuel mix screw to 3 turns out and that brought the rpms up to about 1050. That was the best sweet spot I could dial-in and then I reset the idle at 1,100rpm." Too rich, you should install a #35 pilot jet. You should not be more than 2 turns out. "It meters AIR! " Correct. The mixture screw controls air. Turning it counterclockwise makes the idle mixture leaner. "Ease off the throttle a bit and she screams like a bat out of hell! " This is usually an indication that your main jet is too big. I would install a #140. Are the Jardine muffler and modified airbox the only other mods you are running, or do you have a cam, hi-comp piston, etc.? Sounds like you are doing good. It takes a bit of work but well worth the effort. Hang on. 8-) |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/19/23 at 05:28:16 Thanks Mike. I am considering a 38 and 142. But I don’t want the kabooms to come back. If I was more than 3 turns out, I would make the change right now. Our air in Houston is so hot and humid right now, I’m not inclined to go leaner with smaller jets as a seasonal tuning. We’ll see. I also want to check my gas milage over the coming days. That might prompt me to jet down one size. I’m not 100% certain there are no other engine modifications. I bought it used with no real history. It had the stock exhaust and no carburetor when I bought. The stock exhaust makes me assume no engine mods were done. I do sometimes wonder if the top end was overhauled and perhaps a different cam. Thanks again for all your help! - Paul |
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Title: Re: Evolution of a HotRod - Part 4 Carburetor Post by ThumperPaul on 06/21/23 at 11:32:22 https://www.fuelly.com/motorcycle/suzuki/s40_boulevard/2006#:~:text=Based%20on%20data%20from%2013,0.85%20MPG%20margin%20of%20error. I found this gas mileage study interesting. It has enough size to be a credible study, but the results are heavily skewed towards the dude’s bike that got 56.3mpg on 248 of the total study fuel-ups of 447. One bike accounts for 55% of the study results. If you equal weight each of the 13 bikes, the average drops to 47.5. If you throw out the low (37.1) and the dude that only had 3 fill ups (41.2), the average is 48.72. You can click on each bike/rider to see some detail. City vs Highway and results by fuel-up, any mods, etc. The graphs tell an interesting tale...they are all up and down like a yo-yo... Different driving (city vs highway)? People not filling up exactly the same at each fill-up?? Thought I saw a seasonal pattern for one dude... Things that make you go..hmmmm... I happy to report that I’m right at 48mpg and that includes some weird test riding during tuning. I feel like I’m on par now with the PWK40. I need to get some more fuel-ups, but I've definitely moved in the right direction. Thanks again, Mike! I still may try the smaller 38 and 142, but I want to check out and ride what I have going right now. |
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