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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Did Carb Mods, Still Backfires /cgi-bin/YaBB.pl?num=1431489495 Message started by alienbogey on 05/12/15 at 20:58:15 |
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Title: Did Carb Mods, Still Backfires Post by alienbogey on 05/12/15 at 20:58:15 Hi, We bought a 2007 S40 with 19,000 miles on it for my wife's first bike. It backfired when we test rode it, but we had done our research (on this forum, thanks!) and knew that was common for S-40's and figured we could fix it. So....we went to drill out the brass plug on the idle mixture screw and found it already gone. Hmm, okay, figured we'd leave that alone at first. Then we got into the carb from above and removed the white spacer. There are conflicting threads about whether to replace it with washers and if so how many. We decided to go with two washers which we figured was about half the thickness of the white spacer. We reassembled everything, fired up the bike, and backed out the idle mixture screw while waiting for the bike to begin to stumble, and the dang screw got to almost flush (9 turns) before we heard a difference in the idle. We decided to return it to the original position (we counted the turns carefully). So, today was our first chance to ride it and......it still backfires, perhaps worse than before. Before, when my wife rode it it only backfired on shutdown. Now it will occasionally backfire after downshifting with engine braking. She's using the workaround to pull the choke out for a few seconds before shutting it off, because the backfire scares the heck out of our dog. Any suggestions for our next move or moves? Thanks. |
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Title: Re: Did Carb Mods, Still Backfires Post by Flint on 05/12/15 at 21:04:44 The smallest air leak anywhere in your exaust will cause backfires as well. I doubt if raising the needle will make much difference in how the idle circuit performs. |
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Title: Re: Did Carb Mods, Still Backfires Post by justin_o_guy2 on 05/12/15 at 21:26:16 leak at the head, header/muffler joint, 9 turns on air fuel isn't okay. It can fall out. Add a spring from a ball point . I THINK air,fuel mix relates to the Isle screw. |
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Title: Re: Did Carb Mods, Still Backfires Post by Dave on 05/13/15 at 03:21:13 Backing the fuel mixture screw out more than 3 turns does nothing. Once you reach 3 turns the needle has backed out of the orifice and will no longer restrict flow. You either have something plugging up your pilot jet - or you need a bigger pilot jet. You may have had the idle speed set too high to properly set the mixture screw...it cannot be set if the idle is so high that the slide and jet needle have begun to open. Clean the carb thoroughly and make sure everything is clean. If the bike has the stock air filter box, I would start with a #50 pilot jet. 2 washers and a #150 main. First warm the bike up thoroughly and set the idle mixture screw at 1.5 turns out. The idle should be a bit lower than normal so you can accurately set the mixture. Adjust the idle mixture screw as shown in the video below. The ideal setting listed by Mikuni is 1.5 turns. If you have to back the screw out more then 2 turns - you need a bigger pilot jet. Not just for correct idle - but also for a proper mixture as the carb transitions to the needle jet as the fuel source. If you can turn the mixture screw all the way in and the bike still runs...the jet is too big....more than 2.5 turns out to get optimum idle smoothness - the jet is too small. https://www.youtube.com/watch?v=zm5mB3R8Ucw Once you have the pilot jet set correctly, adjust the idle speed back up to 1,000 - 1,100 rpm. Next the main jet is chosen by making full throttle acceleration runs. I would start with a #150 and see how it runs at full throttle. If it runs well then install the next larger one. If it runs better great....if it burbles or runs slower....go back to the #150 or a #147.5 and see how it runs. Once you have the main jet set the needle is the next place to go. The bike should run smoothly when you just begin to roll on the throttle slowly and accelerate. Ride like you have the Police watching you closely.....or have your wallet sitting on the seat behind you and you don't want to lose it. As you slowly roll the throttle on the bike should accelerate very smoothly...without any hesitation or flat spots. If the bike is lean in this transition the bike will "surge", as if it doesn't know how fast to accelerate. Take washers out from under the needle to make this go away....start with 3 washers and if you feel the surge go to 2 washers. If the bike burbles and sounds rich...add a washer. Backfires - If you have done all the carb jetting properly....then the bike will run properly and any backfires that remain are either part of owning a big single....or you have an air leak in the exhaust system. Backfires do occur if you let the throttle close completely when shifting gears or closing the throttle completely to use engine braking. Loud or unbaffled mufflers make it worse. The backfire comes from closing the throttle completely when riding - which shuts off the fuel flow through everything but the idle circuit....the engine is pulling a lot of air but cannot get enough fuel and the lean mixture cannot be ignited by the sparkplug - but is ignited in the hot exhaust system. Trying to jet the carb to eliminate backfiring is not proper. You jet the carb so the engine runs well. The Carb does have a TEV valve that is supposed to add some additional fuel during the high vacuum situations and help reduce backfiring - I don't think it works well enough with the ethanol fuel that is used today. When you clean the carb make sure the TEV is clean...it is the spring and diaphragm thingy with 3 screws on the right front top of the carb. |
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Title: Re: Did Carb Mods, Still Backfires Post by LANCER on 05/13/15 at 07:01:11 Just a note about "engine warm up time". It is important that the engine be completely warmed up before starting the tuning process. Completely warm means that your bike needs to run at idle for 10 minutes or to take it out for a few miles on the road before starting the tuning process. |
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Title: Re: Did Carb Mods, Still Backfires Post by alienbogey on 05/13/15 at 08:51:53 Thanks a bunch for the replies. Follow up questions: • What's a good source for the different jets? Online or auto parts store or Suzuki dealer? • The bike has rash on the exhaust pipe, so we're thinking of switching to a Harley pipe per the thread in the stickies. I'm guessing it would be best to swap pipes first, and then go through the carb cleaning/jetting/tuning process? • This feels like a dumb question, but when you say "clean the carb thoroughly" are we talking about completely removing and disassembling the carb, or running some sort of cleaning product through it while still on the bike?? As you can tell we're not very experienced with motorcycle maintenance or engines in general, but we have tools and can follow directions and YouTube videos. |
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Title: Re: Did Carb Mods, Still Backfires Post by Dave on 05/13/15 at 08:56:04 Most likely your dealer won't be a good source for jets....unless you have a very good dealer with very good mechanics. Lancer is the best source of jets if you don't know what you need or where to get it. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1336741909 Yes, completely remove and clean the carb. Stuff like Seafoam can be helpful for light deposits...but most likely it needs to be taken apart and cleaned properly. Jetting should be done after the DYNA muffler change. Where do you live? |
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Title: Re: Did Carb Mods, Still Backfires Post by alienbogey on 05/13/15 at 11:09:21 Thanks for the source for jets. I just went out and checked for exhaust leaks. Not knowing any other way to do it, I started the bike and held my hand around where the header pipe plugs into the cylinder, and where the muffler joins the header pipe. I felt no leaks. Is there a better way to check? When we got the bike the one of the header pipe bolts to the cylinder head was pretty loose, and I re-torqued them to specs. (The bike came with a service manual.) So, I'm thinking my wife will keep riding the bike, which really runs okay except for the backfiring, until we can obtain jets and a Dyna muffler (or equivalent). Then we'll dive into removing/disassembling/cleaning the carb, reinstalling, and following the jetting/carb tuning instructions. :P I'll be rather amazed if we put it back together and it runs without a lot of mistakes and cussing. Does the carb have to come off the bike to change out jets? (We live in Gig Harbor, WA) |
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Title: Re: Did Carb Mods, Still Backfires Post by Gary_in_NJ on 05/13/15 at 11:41:25 6964616D666A676F6D71080 wrote:
No, once the tank and seat are removed it can be rotated. But it is easier to work on removed from the bike. With the carb on its side (rotated and still on the bike) it is likely that the float pin will work its way out. Besides, with the bowl removed its a good time to clean the carb...can't really do that on the bike. |
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Title: Re: Did Carb Mods, Still Backfires Post by HAPPYDAN on 05/13/15 at 12:03:06 Hey Alienbogey, I also live in Gig Harbor WA and own and ride a 2012 S40. My S40's workings are all stock, except the air-mix idle screw and petcock. So here's what I have discovered: 1. After-firing and crackling on decel are much worse in cool weather, and before it is thoroughly warmed up. 2 oz of STA-BIL to the tank will reduce this somewhat. If it's +/- 50*F, I just run half choke and that eliminates any issues. 2. The little gas station/store in Ollala, on the waterfront by the bridge, sells non-Ethanol unleaded exclusively. This gas makes my S40 run a whole lot better, and with choke off just "Puffs" on shut-off. Still crackles a bit on a quick roll-off, tho. Suggested mods may be needed to completely eliminate. |
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Title: Re: Did Carb Mods, Still Backfires Post by alienbogey on 05/13/15 at 12:29:44 HappyDan: What a coincidence that you're in Gig Harbor also. Thanks for the tip about the ethanol-free fuel. The fuels business between downtown GH and the Burnham roundabout (can't remember the name right now) also sells ethanol free fuel if that would be more convenient for you. As it happens, just yesterday I filled her tank and mine with some high-octance race fuel leftover from last fall. I'm not going to keep putting that expensive stuff in the bike, but we'll see if it affects the backfiring. |
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Title: Re: Did Carb Mods, Still Backfires Post by Dave on 05/13/15 at 13:26:10 HappyDan....Alienbogey. You both need to go into "My Center" by hitting the icon at the top of the page. Update your information so that your location (City,State) shows up on the left side of the page. You can connect with a whole lot of good folks that way.......... |
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Title: Re: Did Carb Mods, Still Backfires Post by justin_o_guy2 on 05/13/15 at 15:27:35 If the bowl has never been removed from the carb, getting the bolts out with it still on the bike might be harder than pulling the carb. Not having the right tool to remove them will be a certain problem. I can't remember the name, but a number two Phillips won't do it. I ground the tip until the X on the bolt head was filled with screwdriver tip. An impact, really nice. Id be putting some penetrating oil on them every day till you get around to doing it. |
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Title: Re: Did Carb Mods, Still Backfires Post by Kris01 on 05/13/15 at 19:26:33 It'scalled JIS - Japase Industrial Standard. Motorcycle shops should carry them or check Amazon. |
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Title: Re: Did Carb Mods, Still Backfires Post by alienbogey on 05/14/15 at 08:59:32 @ Happydan: I found a pair of brand new Dyna takeoff mufflers, the exact part number recommended to swap. Would you be interested in the other one? (I would have PM'd you, but I don't have enough posts yet) |
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Title: Re: Did Carb Mods, Still Backfires Post by HAPPYDAN on 05/14/15 at 21:23:03 Thanks, but no. I'm an old guy and I like the quieter sound of the stock muffler. I'm waiting patiently for the day someone produces an electric bike with a style and price I like. Met a dirt biker on Green Mountain with an electric dirt bike he bought at Cliff's Cycle Center, and I was impressed with the speed and agility he was able to achieve. As dino oil will run out, it's the way to go. |
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Title: Re: Did Carb Mods, Still Backfires Post by alienbogey on 05/15/15 at 08:37:20 No problem. We're not interested in a louder sound, either, but the stock pipe has rash from the PO and this is a cheap way to get a nice looking pipe. If it's too much louder SWMBO will take it right off. I test rode a Zero electric motorcycle up in Seattle last month. Holy Smokes! Most thrilling motorcycle ride I've had in a very long time. Once the figure out recharging in the time it takes to fill a gas tank it will be all over for dino powered bikes. |
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Title: Re: Did Carb Mods, Still Backfires Post by Art Webb on 05/15/15 at 10:57:53 That's already figured out, if the yabos pushing electric would just frigging admit it got a cordless drill? that's your answer, replaceable batteries go to the 'recharge station' trade your low battery for a freshly charged one, done and done but the idiots that be can't seem to grasp the concept that just leaves...infrastructure dun dun DUUUUN! |
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Title: Re: Did Carb Mods, Still Backfires Post by old_rider on 05/15/15 at 12:25:26 My thoughts exactly, just have a "recharge/exchange station", like they do with your grill gas bottles. Make ALL batteries the same size and connections for ALL vehicles. Have a Drive-Thru exchange station, where you pull in like an oil change station... they pop the door, slide out the used battery, put it in a charging rack, and pull a fully charged one off another rack, install it in the vehicle, pay the fee for a charged battery and off you go. But will they do it? probably not, makes too much sense, and would create a ton of businesses and jobs. But also a few of them would probably buy up old used batteries and cheat a customer..... but you have those type in garages now days anyway. |
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Title: Re: Did Carb Mods, Still Backfires Post by Art Webb on 05/17/15 at 08:11:00 Oh yes As a former pro wrench I makes my blood boil when I hear tales of incompetent / sleazy mechanics costing customers money unnecessarily Though I do tend to look at it carefully before I decide it was a bad job, it's amazing what gets blamed on mechanics sometimes "he put a fuel pump in and then the brake master cylinder went bad, I think he rigged it to go out" "That's not actually possible" lol having an accurate charge gauge on the car would help mitigate this somewhat, a bad battery would I think sow less than a full charge |
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Title: Re: Did Carb Mods, Still Backfires Post by justin_o_guy2 on 05/17/15 at 10:24:14 I fixed copiers and cash registers for 7 years. Call comes in, paper jam... Go fix the paper feed problem,tomorrow copy quality falls off, and, totally unrelated, yet, all my fault. Somehow, while I was cleaning paper feed tires and clutches I somehow managed to set up a time delay sabotage to cause the copy quality to go to crap.I was so busy I got to work early, rarely had time for lunch, worked late, but they didn't know that. Maybe they thought it would be free,,and sometimes it was... if the wrong person took the call and called it a Callback. There were idiots who answered the phone. |
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Title: Re: Did Carb Mods, Still Backfires Post by DavidOfMA on 05/18/15 at 20:23:31 For what it's worth, I'm at sea level near Boston and my 2009 S40 popped very frequently on decel. I checked for exhaust leaks, cleaned the carb, used a richer jet, and tinkered endlessly with the idle mix screw, and none of these things eliminated the decel pops. However, clipping 1/2 round off the spring in the TEV (Transient Enrichment Valve) on the right side of the carb has virtually eliminated them, with a negligible effect on gas mileage. Instead of one or more pops almost every time I decelerated from more than 40mph, I get one or two mild pops, at most, on a three-hour ride. I'd try everything else recommended here before tinkering with the TEV spring, but it worked for me. |
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Title: Re: Did Carb Mods, Still Backfires Post by UneSauvage on 05/31/15 at 09:27:05 There's a rubber cap (sorry, I'm not very technical and don't know what it's called, but I can show it -- it's near the left edge of the photo about 1/3 down from the top) that on my '04 had become dryrotted and cracked. This was letting air in and when the tech pinched it, RPMs went up and when he replaced it, backfiring decreased by about 30-50%. Check that rubber cap at the intake and replace if needed. |
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Title: Re: Did Carb Mods, Still Backfires Post by KennyG on 05/31/15 at 13:25:05 David OF MA Were you able to work on the TEV without removing the Carburetor? Kenny G |
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Title: Re: Did Carb Mods, Still Backfires Post by DavidOfMA on 05/31/15 at 14:24:14 Yes, just remove the three screws on the TEV cover. Maintain some pressure on the cover or the spring will pop off and get lost. Clean the passages and do other carb adjustments before you experiment with the spring, and remove only small amounts. Cutting off only 1/2 round was just right for my bike. |
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Title: Re: Did Carb Mods, Still Backfires Post by KennyG on 05/31/15 at 14:54:08 David, Thank You. I was able to get the screws out and one at a time and replaced them with Socket Head Cap Screws. Tomorrow I will pull it apart and work on the spring. Kenny G |
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Title: Re: Did Carb Mods, Still Backfires Post by alienbogey on 06/01/15 at 10:58:46 Lots of good info/suggestions. Our first step will be cleaning the carb and re-jetting. We ordered the jet kit from Lancer, but he was out of the 50 which, naturally, is what we need. So, we're standing by to receive it before we tackle the project. |
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Title: Re: Did Carb Mods, Still Backfires Post by KennyG on 06/01/15 at 11:10:21 Today I pulled apart the Transient Enrichment Valve and cleaned everything and blew out the tiny hole with carb cleaner and compressed air. Since I had an Ace #90 Spring I replaced the Mikuni Spring with the Ace instead of cutting down the factory spring. The Ace spring is about a third shorter in length than the factory spring Results: I had to increase the idle speed quite a bit, perhaps a turn on the idle speed screw, maybe more then a turn. I had absolutely no popping on deceleration. None what so ever. Slight popping when changing gears going up through the gears. No popping when going down through the gears. There was a very slight hesitation when the engine returns to idle, the idle speed dips just a trifle. I increased the idle speed to about 1350 RPM on my Ryca Tachometer and that appears to have smoothed out the transition from cruising speed to idle speed. I went for a 47 mile ride on rural roads with a lot of shifting and braking and accelerating. The results appear to be an improvement. When I arrived home I turned down the idle speed to as low it would go before stalling. I then re-adjusted the idle speed screw. This adjustment is not as sensitive as it was before the spring change. But turned it in until the idle started to stumble and then turned it out until it almost choked. I then moved the screw half way between the stumble and choking conditions. After the next test ride I may be able to slow down the idle a bit. I am going to leave well enough alone for a tank or two of fuel. What is needed here is a Progressively Wound Spring. I am going to search the new Ace Hardware Store that just opened for a variety of progressive wound springs. Update: Went for a 20 mile ride this evening and was able to slow the idle down to about 1275 RPM. The adjustment that I made to the idle air screw earlier today corrected the idle dipping down in speed and hesitation when coming into a stop. I think this is as good as it is going to get. Kenny G |
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Title: Re: Did Carb Mods, Still Backfires Post by justin_o_guy2 on 06/01/15 at 11:36:54 I had absolutely no popping on deceleration. None what so ever. I would have to work on that some more. |
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Title: Re: Did Carb Mods, Still Backfires Post by KennyG on 06/04/15 at 20:55:17 I filled the gas tank this evening and checked my gas mileage. The last few tanks I averaged 47 miles per gallon. The tank today I only got 44 miles per gallon. I guess I am going to run a couple more tanks through to see what kind of mileage I get before I change anything else. If mileage doesn't return to 47 mpg I will then look around for a couple of different Progressive Wound Springs at Ace Hardware. I suspect that I am using more fuel during deceleration because the Transient Enrichment Valve is activating more quickly with the #90 Spring, thus using more gas. I can live with this level of MPG rather then listening to the after firing if I have to, but I want to get the maximum MPG possible. Kenny G |
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Title: Re: Did Carb Mods, Still Backfires Post by justin_o_guy2 on 06/04/15 at 21:52:23 Well,Kenny, I had a cam, bigger jets, gutted header, only the outside pipe, Supertrapp w/14 disks and rode the snot outta that thing, I got 49,, My girl got 51. I never messed with the TEV,, The low growling and snarling sounded great. No gunshot between gears, sometimes a muted whoof on shutting down. I could ride by horses or by a hospital, the noise level was not getting me dirty looks at intersections. |
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Title: Re: Did Carb Mods, Still Backfires Post by KennyG on 06/04/15 at 22:03:27 Justin, All of my riding is on the rural roads of North Texas and I am constantly braking and changing gears so I don't expect to get the best possible gas mileage that an S40 can get. Sometimes I don't even hit fifth gear for 10 or 15 minutes at a time. I am satisfied with 47 MPG, naturally I would like better mileage Kenny G |
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Title: Re: Did Carb Mods, Still Backfires Post by justin_o_guy2 on 06/05/15 at 06:53:34 Well, I was running into town and my roads s allowed speeds that made fifth part of it. If you're wringing it out and having fun and you're downshifting and cornering and accelerating and then its time to drop a gear And do it again, your 47 is fine. And you otta be giggling. That is the kind of road where you can pick a corner and focus on one corner, play with different entry lines and exits and see if you can get consistent. I was grinding pegs, but one day hit a corner and I leaned out more and the bike,less, and it felt smoother and faster. I never got consistent,really, except for the fun. |
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Title: Re: Did Carb Mods, Still Backfires Post by Art Webb on 06/05/15 at 07:54:53 I average 45 mpg right now, but that may have to do with my mid-range being finicky so I ride with the throttle open more |
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Title: Re: Did Carb Mods, Still Backfires Post by KennyG on 06/08/15 at 17:32:20 June 8, 2015 Today I removed the Ace Hardware #90 Spring and replaced it with an Ace #86 Spring. The #86 Compression Spring is cone shaped and is the closest thing that I can find to a Progressively Wound Spring. The major diameter is about 1/2" and the overall length is equivalent to the #90 Spring, about .700. The smaller diameter is about 1/4" OD. By "feel" I cannot tell if the #86 Spring is softer or more rigid than the #90 Spring, but I think it is more rigid. The spring fits best in the diaphragm if the smaller diameter goes in first. The first thing that I noticed after starting the engine was that the idle speed was 2000 RPM, so I suspect the #86 Spring is more rigid than the #90. I slowed the idle down to about 1200 RPM and went for a test ride. I had just a little more popping with the #86 than with the #90 Spring when up shifting. There is very little intermittent popping on down shifting, but still no popping on deceleration. When I returned home I adjusted the Idle Air Screw using the accepted procedure, and then reset the idle speed to about 1150 RPM. The idle air screw is now turned out about 2 1/4 turns. I went for another test ride and there is still a small amount of popping when up shifting. Once in a while there is a little popping on deceleration. I am sure that true progressively wound spring with the soft end facing out will correct this situation, but it is going to take some time to find a supplier who will sell me a few springs of various wire sizes. The after firing is so much improved over how it was initially that I am happy with the results. I am going to leave well enough alone for another tank or two of fuel. The next test I want to try is adding a washer under the Ace #90 Spring. If anyone has any ideas as to where I can procure a few Progressively Wound Springs I am interested in hearing from you. Kenny G |
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