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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Cutting out / stumbling at highway speeds? /cgi-bin/YaBB.pl?num=1506034948 Message started by Jeremy on 09/21/17 at 16:02:28 |
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Title: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/21/17 at 16:02:28 So after putting the Savage on a major diet, I have my '96 back together and I'm loving it. I swapped out all the airbox junk for a Ryca cone style filter and a little Biltwell muffler on the stock header pipe. Ordered Lancer's kit, and I bumped the pilot jet up to a 55 and the main to a 150. Also did the white spacer mod. The petcock has also been replaced with whatever the board recommended alternative part (from a Raptor?) is. Other than the jetting stuff, petcock, intake, and exhaust, the engine is totally stock. Bike idles fine and starts up fine with no choke. Runs fine and seems to accelerate fine at normal speeds (like driving around on 35 or 45mph roads). Performs well up to around 50mph. The problem is when I'm hitting highway speeds or really getting on the throttle, the bike stumbles. Almost like it cuts out for a split second, then picks right back up, which gives it sort of a "surging" feeling. This happens if I'm holding a constant speed (like in the 60+ mph range) or if I'm accelerating hard. When holding a constant speed, it does it pretty frequently, like 3 times in 10 seconds, but sometimes it will be fine for a mile or two. I'm able to run at an indicated 70 or 75mph, so it isn't like the bike is completely neutered or incapable of speed. My next idea is to bump up one more size on the main jet, since I have such a free flowing intake / exhaust setup. Thoughts? |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Dave on 09/21/17 at 18:47:39 Jetting is a trial & error type event. You try something and see if the bike runs better...or worse. You adjust the pilot jet first. When you adjust the mixture screw for the smoothest running, it should be 1.5 - 2 turns out. More than 2 turns and you should install a larger jet - if you can turn the screw all the way in an the bike is still running smooth, you need a smaller jet. Then you adjust the main jet. You go for a ride and once the bike is warmed up, pick a nice long hill and get up to about 40 mph in high gear and apply full throttle. As the bike accelerates it should pull smooth and strong. If you begin to roll off the throttle and you feel the bike accelerate a bit harder - you need a smaller main jet. If you roll off the throttle and the bike slows - you may need a larger jet....or it might be OK. I keep installing larger jets until I can feel the bike is has gone a bit sluggish and sounds rich.....then I put in a smaller size or two. The last thing you adjust is the height of the needle. You adjust for smooth operation at light throttle settings - if the bike surges at slow acceleration or slow speed cruising - raise the needle. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by IslandRoad on 09/21/17 at 19:12:45 Dave, that is the most succinct set of instructions, for carb tuning, I've ever read on this site. That post should be made into a sticky! |
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Title: Re: Cutting out / stumbling at highway speeds? Post by batman on 09/21/17 at 20:22:25 Sorry, but I checked out the biltwell mufflers ,and they aren't built well,at least not for our bikes ,they have no baffle and therefore no backpressure ,their like a straight pipe which makes carb tuning very hard,and performance at higher speeds suffers because you basically added the length of the muffler to the header pipe length(32"+ muffler) ,longer header pipes favor low rpm ,shorter favor higher .That 's why the bike runs OK at low speeds but will only achieve 70-75 ( a stone stock bike will do 85) .Cone filters have been known to block off part of the throat when mounted directly to the carb ( the oval opening at the top controls the slide ,if blocked it will cause the slide to open slowly ,leaning out the fuel mix until it catches up,if it catches up. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/22/17 at 03:28:52 Thanks for the advice, Dave! I'll see if I can head out this weekend and try that. Unfortunately, in my mess of a garage, I can't seem to find the rest of Lancer's kit >:( Have to see if I can dig the rest of the jets out from wherever I put them. Batman, I was thinking about the back pressure issue when I bought the Biltwell, but I figured I'd give it a go, since the look of the Biltwell was exactly what I wanted. I may give a shot at welding up some "lollipop" baffles and seeing if that helps. It sounds like ultimately, that may be my problem. The bike may have done higher than the 70-75 that I got it to, but (much like the Ninja 250 that I used to own) I hate pushing a bike on the highway when it sounds like it's about to explode. In my head, I know the bike can take it, but I'm used to sportier bikes that can sit at 80mph for hours and not break a sweat. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/22/17 at 03:32:39 Also, if it makes a difference, the cone filter is mounted on an elbow that bends down behind the engine, not directly to the carb... http://https://photos.smugmug.com/Other/Savage/i-5CvTPzk/0/0e58a188/M/IMG_1615-M.jpg |
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Title: Re: Cutting out / stumbling at highway speeds? Post by justin_o_guy2 on 09/22/17 at 04:54:55 https://www.bing.com/search?pc=SOWI&form=AMZNS2&q=engine+intake+design+theory |
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Title: Re: Cutting out / stumbling at highway speeds? Post by LANCER on 09/22/17 at 06:03:27 Keep in mind too, that a muffler should be 3x the volume of the engine, ideally, and with a decent amount of baffling. That is why many find the HD Dyna muffler to work very well with our engine. And it is cheap. Or if you desire, a Supertrapp or Cone Engineering make good ones as well, but you pay more. Supertrapp is the most expensive. You will find that with these mufflers the tuning/jetting will be easier and you will like the results too. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/22/17 at 07:12:35 Thanks, Lancer. My guess is the muffler is a big part of the problem. I may take a shot at constructing some sort of baffle for it. At the very least, I think the neighbors will appreciate that :) |
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Title: Re: Cutting out / stumbling at highway speeds? Post by verslagen1 on 09/22/17 at 07:31:17 You should turn that intake elbow around, straight portion nearest to the carb. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by batman on 09/22/17 at 08:07:57 I agree with Vercy,also the length of the intake matters,checkout ; www.bgsoflex.com/intakeln.html ( be aware that the intake length is the total length between the intake valve through to the air filter - 1/2 the inside diameter of the hose your using.)You might try what we do to restore the baffles in a Dyna muffler ,that is to drive a soft plug (the kind used in to plug the water jackets on auto heads) half way down your muffler ,forcing the exhaust to move around the baffle giving you some back pressure,pick the proper size and drive it in from the forward end.If you find it to be to much you can drill a hole in the center of the plug start small and drill larger if needed,go slow as the noise will increase and the backpressure will drop as the hole gets larger.You may see a lot of bluing on the muffler as the exhaust gases are forced around the baffle ,how much will depend on the Biltwell. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/22/17 at 08:42:31 Awesome info! I'll look into all of that. Vers, do you mean just swing the intake to 3 o'clock (so it sticks out the side) instead of 6 o'clock (hanging down behind the engine)? |
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Title: Re: Cutting out / stumbling at highway speeds? Post by batman on 09/22/17 at 08:51:10 No , I think he means the longer straight section should be attached to the carb,as this straightens the air flow into the mouth of the carb.(ideal)Right now the air tends to hug the outside of the elbow making the air denser at the top as it enters the carb,but the slide opens from the bottom ,and that is where the air needs to be to readily mix with the fuel.(the carb is at part throttle ,slide less than half open @ 60MPH, most of the time during normal driving ). |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/22/17 at 09:27:16 Gotcha. That makes sense. Not sure if it's possible, though. I think the end that fits onto the carb intake is slightly flared (intake and filter must be slightly different diameters), so I don't know that it's flip-able. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by justin_o_guy2 on 09/22/17 at 09:30:41 People modify things that they have never studied. It's not hard to read a little. Ever notice how much better it is having a big straw in the malt? Intake changes have a big impact because there is no piston shoving air out, it's creating a low pressure area and if the design doesn't make it easy for air to flow and get gasoline dispersed evenly through it, it's not a great intake design. There's a link to a header design video that is really good, but I don't know where it is. My intake design link may not be the best out there. 485751564B4C7D4D7D45575B10220 wrote:
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Title: Re: Cutting out / stumbling at highway speeds? Post by batman on 09/22/17 at 11:53:53 Jeremy,if you still have the original rubber tube, you could use that to come off the carb and a piece of PVC pipe for the rest? |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/22/17 at 15:57:21 Good idea. Worst case, I can definitely cut a lot of the length off of the intake that's on there now and try to get the cone filter much closer to the carb. Also found the rest of the jets that Lancer sent, so I've got those to try out as well. Got my hands full of stuff to test! |
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Title: Re: Cutting out / stumbling at highway speeds? Post by justin_o_guy2 on 09/22/17 at 16:00:11 Wow,, |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/22/17 at 17:06:21 Cut a good chunk off of the intake, which should shorten up the intake path, as well as smoothing out that elbow as much as possible. http://https://photos.smugmug.com/Other/Savage/i-xzWNZnP/0/896084d2/L/DB613969-27D8-4D8A-A683-CE805BCF7DCE-L.jpg |
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Title: Re: Cutting out / stumbling at highway speeds? Post by antmanbee on 09/22/17 at 19:08:12 This is what I did. A longer straighter smooth intake flow into the carb is usually better. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/23/17 at 03:21:51 Yeah, that looks much better. Gonna try to hit the hardware store this weekend and see if I can come up with some parts to fab up a baffle. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by madmikesmech on 09/23/17 at 10:45:58 152F303D32380E333D385C0 wrote:
I must agree IslandRoad, great tech tip Dave... forward and to the point!![ch128077] |
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Title: Re: Cutting out / stumbling at highway speeds? Post by madmikesmech on 09/23/17 at 11:10:02 6B52555340484F210 wrote:
Great looking build Jeremy!! I'm looking to head the direction of that look for the one I have "on the table" now! I was lucky enough to score 2 garage find fixer uppers not long ago. The daughter wants us to get one running for her, and the other is aiming for that lean bobber look youve obtained! But where is your battery? Or do you push start it?!! |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/23/17 at 11:25:41 Thanks, Mike! It isn't a look that everyone likes, but I wanted as lean and clean as possible. Pretty happy with how it came out. Battery is mounted in a little battery box that I bent up / welded. It sits on a little bracket, just forward / under where the swingarm mounts to the frame. It's that blue thing you can see in the picture right above the muffler. A little LiPo battery. If you have any questions at all about mine, just ask. Not necessarily explanatory, but here is the gallery of all the pictures I took during the build... https://jstrain.smugmug.com/Other/Savage/ There are some pictures of the battery box (which also functions as a muffler mount) in there somewhere, but I'm happy to snap some more detailed pictures if it'll help you out! |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/24/17 at 08:04:29 So the reshaped / shortened intake didn't help at all. Still cutting out on the highway Next step is trying to do something with the muffler. I may give a shot at Batman's idea with the water jacket plug. I think I can buy a replacement baffle (which you can't really call a baffle in the first place ;D ) for cheap, which should make it easy to fiddle with off the bike. If this helps troubleshooting, here is a picture of a new plug that I put in just before this morning's ride. The ride was about 10 miles and involved a bit of highway, some surface street speeds, and some sitting in traffic. Not sure how long you need to run a plug before you get a reliable reading. http://https://photos.smugmug.com/Other/Savage/i-zMBPjLT/1/1f663db4/X2/91FFF01B-4B44-4921-8DBE-A03D8B8231EA-X2.jpg For reference, this was the plug that was in the bike when I bought it and has been in use up until this morning... http://https://photos.smugmug.com/Other/Savage/i-PVHWcCb/1/70f92795/X2/ED7F810B-0046-4551-8B93-CAF031225620-X2.jpg |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/24/17 at 09:47:47 Also pulled the petcock off and checked the filter screens just to be sure it they weren't clogged. Both screens looked nice and clean. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by batman on 09/24/17 at 18:44:52 The porcelain tip of the plug should be light tan from the tip all the way down into the plug to where it meets the metal(even after many miles) your running very rich if it looks like that after 10 miles. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/25/17 at 02:53:22 The top picture (with the pliers holding the plug) is the fresh one with just 10 miles. That one looks rich? |
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Title: Re: Cutting out / stumbling at highway speeds? Post by batman on 09/25/17 at 06:25:11 Sorry ,can't really tell ,from what I can see it looks OK ,but I can't see down inside ,but porcelain should be "clean" with no soot all the way to it's base. the color will turn to a light tan over time (more miles).if it remains bright white then your running lean. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/25/17 at 07:15:55 Gotcha. The second pic was the old plug that I took out. Could be the original for all I know. I’ll keep the current one in for a while and give it another look after more miles. In the meantime, I’m gonna check some other issues like making sure the gas cap vent is clear, float height, and my fuel hose. I think it might be some 1/4 inch that I had handy. Have some 5/16 coming in the mail. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by justin_o_guy2 on 09/25/17 at 09:09:49 Clear tubing on the bowl drain curled up next to the bowl, open the drain, it'll show you the fuel level. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/25/17 at 09:54:18 Is it possible that’s if the float level is too low, it can’t feed enough gas at high RPM? I’m used to the opposite problem where the float let’s too much gas into the Bowl. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by justin_o_guy2 on 09/25/17 at 10:13:19 27383E3924231222122A38347F4D0 wrote:
Check it. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Ruttly on 09/25/17 at 12:30:11 JOG your a pretty fart smeller I mean smart fella ! ;D |
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Title: Re: Cutting out / stumbling at highway speeds? Post by justin_o_guy2 on 09/26/17 at 10:07:24 I Wish I had been the guy who came up with that. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Ruttly on 09/26/17 at 12:11:19 JOG, That will only work if atmospheric pressure is the same at the end of the tube and in float chamber ! In other words float bowl vent must be clear ! Great way to check it , wish I thought of it too ! ;D |
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Title: Re: Cutting out / stumbling at highway speeds? Post by justin_o_guy2 on 09/26/17 at 12:17:30 What would cause a bowl of fuel with a coupla jets between it and the carb throat to have a pressure differential between it and atmospheric pressure? |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Ruttly on 09/26/17 at 15:10:46 I smell wood burning ! I knew I could get you thinking ! If the needle was seated and the pilot and vent were plugged. What if ? :-? |
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Title: Re: Cutting out / stumbling at highway speeds? Post by batman on 09/26/17 at 15:36:13 What if both vent hoses on the bowl were plugged,and the needle was all the way down and the pilot jet was plugged,and the bike is under water but the open end of the hose is above the surface?HUH! |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Ruttly on 09/26/17 at 19:36:00 Batman , Now we really got him confused ! But I think you have to be south of the equator for it to happen like that ! :-/ |
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Title: Re: Cutting out / stumbling at highway speeds? Post by batman on 09/26/17 at 21:24:49 Well I think Jeremy is the one confused,he shortened the intake to the carb so much he might as well have put the air filter right on the carb ,it wouldn't be any worse ,and he still hasn't done anything with the muffler,and doesn't know that a lollypop baffle won't help all that much. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by justin_o_guy2 on 09/26/17 at 21:33:08 That Intake Theory didn't matter. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/27/17 at 03:54:34 Been pretty busy lately, so I haven't had time to do much of anything. I did put on 5/16 fuel hose and checked the float height, which seemed fine. I ordered a replacement baffle for the Biltwell, but it hasn't even shipped yet. Once that comes in, I can measure the ID and see about getting a plug for it, then swap it into the muffler. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by Jeremy on 09/27/17 at 04:46:50 Regarding intake length, is there a prescribed length that I should shoot for? Now that I have that 90 degree bend smoothed out some, I should be able to get a joiner and extend the length of the intake further, keeping a nice straight path right underneath the frame. |
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Title: Re: Cutting out / stumbling at highway speeds? Post by batman on 10/02/17 at 22:53:19 Jeremy gave you a way to find the length back on page 1,use the sight I suggested, to find rpm range you find useable ,divide rpm by 68.3 to give you the speed ranges. I used 17 " on the chart, but cut the intake length to 16'' ,1/2 the dia. of the 2" pipe I used to make the intake. |
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