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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> My backfiring / rejet / dyna muffler adventure /cgi-bin/YaBB.pl?num=1246892678 Message started by trapper_canada on 07/06/09 at 08:04:38 |
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Title: My backfiring / rejet / dyna muffler adventure Post by trapper_canada on 07/06/09 at 08:04:38 Well I think I have resolved (mostly) the backfiring problems on the wifey's S40. I learned a lot reading through the posts here. I'm gonna provide a brief summary of the steps I went through in case it provides any help to others. Everything I did was referenced on other posts to some degree. It all started with the nasty backfire. It was ALL the time. The first thing I did was the white spacer mod. Replaced the stock spacer with a #4 nylon spacer that I got at the hardware store. I had some trouble trying to get the carb out. So after reading here I decided to spend a couple minutes to remove the battery box (4 bolts inside). Should have done that right away as it gave so much room to take the carb out. I was fortunate in that all the carb screws came out easy. As recommended, I replaced them all (4 on top and 4 on bottom) with hex cap screws. When backfiring continued, I noticed a HUGE exhaust leak where the stock muffler attaches to the header. Instead of trying to fix that I thought it would be a good time to replace the muffler with a stock Dyna muffler. I removed the full exhaust in order to have more room to fit the Dyna muffler. The opening of the Dyna muffler was a bit loose to fit the head pipe, so I cut up some aluminum cans and used some High Temp RTV sealant. The dyna mounting points fit on the S40 support bar. I used two carriage bolts and was done. I fired up the bike, and the backfiring was still bad. Time to rejet. I bought a Stage 1 kit from DynoJet (if I could go back I would have taken people's recommendations and gone with Lancer's kit as the DynoJet costs more and does not include a larger Pilot Jet). I put in the jet DynoJet recommended. It was easy to do with the new hex screws. Took all of 5 minutes. Backfiring was still there...but it was different. It was now firing on accel instead of just decel. However even with the backfiring, the engine ran nicer and I could feel more power when I took it for a spin. So...after further investigation I found that it was leaking at the head (where head pipe meets cylinder). I tried tightening it and it helped..but just a bit. I read that loosening and then re-seating it might help (I should mention I put in a new exhaust gasket as well). I removed the full exhaust and this time tried to make sure that the head pipe gets seated and secured better first. When I did that I realized that when you put on the Dyna muffler the line of the exhaust is not true to stock. I had used two carriage bolts to secure the Dyna muffler and that forced the exhaust to be mis-aligned. To make it a better fit, I just used the front bolt on the muffler. That helped. I tightened everything up...and no backfire. Woohoo. We took it on a 40 mile test run..highway and city to see how it held up. the additional power was very noticeable. We had 1 or possibly 2 backfires...but they both occurred on hard deceleration / downshift from 65mph to 0. We can live with that. As the alignment of the exhaust is still possibly out a tad, there could be a small exhaust leak. We may look at going with the bigger pilot...but we need to run more to see how it goes. We put the stock heat shield back on but could only use one clamp as the other is affixed to the stock exhaust. It looks like it holds pretty tight. When I went to put the heat shield by the footpeg back on I saw that it was pretty tight. To fix that I put in a couple washer/spacers in there to lift it away from the exhaust enough. So that is my story :D |
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Title: Re: My backfiring / rejet / dyna muffler adventure Post by Serowbot on 07/06/09 at 08:55:07 Yeah!..... Sounds like you got it pretty good. Watch out,.. you've caught the bug now.... ;D |
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Title: Re: My backfiring / rejet / dyna muffler adventure Post by Boule’tard on 07/06/09 at 09:05:30 All right! Congratulations on getting that sorted out [smiley=thumbsup.gif] So true.. the smallest leak (as in, your fingers are close enough to the pipe to burn them before you feel the little puffs) will cause it to backfire. I had to shim out the header to match the Dyna muffler and over-torque the header bolts too. |
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Title: Re: My backfiring / rejet / dyna muffler adventure Post by odvelasc on 07/06/09 at 19:41:09 Well done, now get yourself a little 7inch heatshield for the exhaust. It makes the bike look cleaner. Try a local custom shop, or JCwhitney. Shouldnt be more the 20$ or so. Did you use the 146 main from the dyno kit? Make sure the muff is stabilized to the frame with a mounting bracket or it will come loose at the header as mine did. |
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Title: Re: My backfiring / rejet / dyna muffler adventure Post by Boule’tard on 07/06/09 at 20:03:43 707B697A737E6C7C1F0 wrote:
PAH!! >:( HEAT SHIELDS FOR SISSEYS http://i30.tinypic.com/raqbs4.jpg Eehhehh what was that part number again? [smiley=vrolijk_1.gif] |
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Title: Re: My backfiring / rejet / dyna muffler adventure Post by trapper_canada on 07/07/09 at 09:42:11 53584A59505D4F5F3C0 wrote:
Yes I want to get a smaller exhaust shield. I have a longer one that won't fit. Might see if I can get a buddy to cut it and redo one of the clamps. I have the dyna muffler affixed to the stock muffler bracket...its not going anywhere. |
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Title: Re: My backfiring / rejet / dyna muffler adventure Post by odvelasc on 07/07/09 at 10:33:50 7C7A6978786D7A576B6966696C69080 wrote:
put a pic of your job :) |
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