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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Still back firing after rejet /cgi-bin/YaBB.pl?num=1253711311 Message started by DesertDweller on 09/23/09 at 06:08:31 |
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Title: Still back firing after rejet Post by DesertDweller on 09/23/09 at 06:08:31 2005 S40 , took out the last baffle in the muffler and replaced the air filter with a mesh steel one. Installed the dyna stage one kit, their 144 main jet and later the 146, tried with the little white washer , a smaller one then just a small #4 and now no washer, and it still backfires after closing the throttle and engine braking all the way to a stop, not just pop pop pop but a really load baaang , scares the crap out of people at the traffic light lol. What else can I do? :-/ |
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Title: Re: Still back firing after rejet Post by Charon on 09/23/09 at 08:19:50 I am sure someone will correct me if I am wrong. You do not have a "backfire". You have an "afterfire". A backfire is when the flame makes its way back through the intake side of the system into the intake manifold and carburetor. However, the "afterfire" is usually, though incorrectly, called a "backfire". On closed throttle deceleration the engine vacuum goes quite high. The throttle slide is closed, so little air passes (which is why the vacuum is high). The throttle slide being closed, the needle pretty much closes off the main jet. The high vacuum pulls excess fuel into the manifold via the pilot (idle) circuit, and with little air the mixture is probably rich. This rich mixture may or may not burn properly in the engine. If it doesn't, it makes its way into the hot exhaust pipe. Once the engine finally gets a burnable mixture and fires, the flame from the exhaust valve can ignite the fuel in the exhaust, and you get the afterfire. Making things worse, the fuel in the float bowl tends to move slightly forward on deceleration (or lots forward if you brake hard). The passages to the pilot are in the front of the float bowl, so the mixture tends to get richer yet. It seems odd that the mixture will go rich on deceleration, since Suzuki jets the pilot lean to meet EPA regulations, but I think that is what happens. I may be wrong, but I think the simplest remedy is to turn up the idle, which will reduce the engine vacuum on overrun by not allowing the throttle butterfly to close quite as far. |
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Title: Re: Still back firing after rejet Post by DesertDweller on 09/23/09 at 08:36:30 I hear you, I am going to try that |
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Title: Re: Still back firing after rejet Post by justin_o_guy2 on 09/23/09 at 08:41:32 Charon, IDK if thats exactly "It", but it sure sounded good. Ive never even tried to wrap my head around the exact mechanism that causes the popping & barking, because I dont think I could have ever figured that out like that. IF thats not right on, you sure coulda fooled me,. Excellent post.. |
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Title: Re: Still back firing after rejet Post by Oldfeller on 09/23/09 at 08:53:30 Hard engine braking on an exit ramp from interstate full speed run will cause the same sorts of shuffling-whapping-bapping nonsense. Simply dialing in a tiny bit of throttle will stop it instantly. Another part of the puzzle is very high full run exhaust temps that can cause burn detonation starting from the end of a shorty muffler (where air and oxygen can mix with the exiting fuel rich exhaust letting it combust on exit). Watching Toymakers short can exhaust at the first Dragon run was a lot of fun -- made small flames and a lot of whapping and bapping noises on exiting the interstate. I used to tease him about it but I can't say much about it now as I whap-bap now too. |
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Title: Re: Still back firing after rejet Post by DesertDweller on 09/23/09 at 09:47:06 I chnged back to a smaller jet, put the white ring back in, upped idle rpm, but no luck yet, yes opening the throttle will solve the problem, but I forget and the result is a loud bang.... Thanks form your input guys, I'll keep trying stuff, maybe steer away from the Dyno jets. |
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Title: Re: Still back firing after rejet Post by Serowbot on 09/23/09 at 10:44:29 Desert Dweller,.... in which desert do you dwell?.... :-? |
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Title: Re: Still back firing after rejet Post by verslagen1 on 09/23/09 at 11:30:38 With your mods it'll hard for anybody to give you perfect advice. I go about like this, adjust the Idle mixture for the shutoff bang, should be a little poof. Use the WOT steady speed back off test for the main, white spacer mod to tame any flat spots. next check the exhaust for leaks. use a candle flame to find the little buggers. I find that exhaust leaks are usually responsible for shift bangs especially if your idle seed is too low. |
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Title: Re: Still back firing after rejet Post by DesertDweller on 09/23/09 at 14:12:57 485E49544C59544F3B0 wrote:
Tucson, like you! |
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Title: Re: Still back firing after rejet Post by DesertDweller on 09/23/09 at 14:15:16 5E4D5A5B44494F4D4619280 wrote:
Thanks I,ll look for exhaust leaks, thinking of getting a screaming eagle from ebay, maybe that'll help too 8-) |
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Title: Re: Still back firing after rejet Post by FreeSpirit on 09/23/09 at 14:36:02 DesertDweller....Just for info,There's a small group here of Savage riders close to you,or at least in Arizona :) About four of them,I think.Maybe more :-/ |
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Title: Re: Still back firing after rejet Post by vtail on 09/23/09 at 15:46:01 Try a 152.5 main and no spacer |
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Title: Re: Still back firing after rejet Post by odvelasc on 09/23/09 at 18:21:58 3C2F3839262B2D2F247B4A0 wrote:
+1 on the bangs on decel |
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Title: Re: Still back firing after rejet Post by DesertDweller on 09/23/09 at 19:04:31 4D796E6E587B6279627F0B0 wrote:
That's cool Free, maybe I'll see them here! 8-) |
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Title: Re: Still back firing after rejet Post by DesertDweller on 09/23/09 at 19:05:10 2321343C39550 wrote:
I am getting different jets as we speak, thanks. :) |
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Title: Re: Still back firing after rejet Post by Serowbot on 09/23/09 at 23:15:42 1D3C2A3C2B2D1D2E3C35353C2B590 wrote:
Tucson, like you![/quote] Well, why didn't you say so?... ;D 3 or 4 of us here are riding up to Superior Az. on Oct 10th to meet up with a Phoenix member, Johnboy... Feel like a ride?... about 100 miles each way... Serowbot BTW,.. this is the right place for gettin' your bike fixed up,... but most of the hangin' out, goofing off, and meeting up, is in the cafe section... 8-) |
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Title: Re: Still back firing after rejet Post by DesertDweller on 09/24/09 at 06:33:20 I'll email you. |
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Title: Re: Still back firing after rejet Post by DesertDweller on 10/09/09 at 12:42:05 To close this out on a positive note, it's fixed no more backfire/afterfire Thanks to everybody with advice. It seems to have been the header bolts that were slightly loose.... Installed a Screamin Eagle , tightened everything down and sealed the header to pipe with exhaust goo. Did the carb adjustments per Lancer's post, did the white spacer mod for the 8th time and voila, sounds awesome runs great and no more bangs. Main jet: Dyna 144 Pilot #55 1.5 Turns on the pilot screw and 1 #4 washer on the needle. Thank you Thank you Thank you 8-) 8-) |
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Title: Re: Still back firing after rejet Post by justin_o_guy2 on 10/09/09 at 12:46:09 Great News! Glad you got it nailed... |
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