 Backfiring... carbs?
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Joined: Jul 2006
Posts: 112
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OP
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Joined: Jul 2006
Posts: 112 |
Hi all...
I have removed the first baffles from my stock TBA slashcuts and have put two holes in each of the 2nd. The sound is considerably better but I am getting some popping on decel. Also a bit of a power reduction. I rode to work yesterday (about 20 miles). When I hit the starter button 8 hours later to go home it backfired really loud.. which in our underground parking structure sounded like war. I had heard that removing the first baffle shouldn't require any tweaking. Is this common? Carb adjust only or more?
I'd appreciate any input.
Chris
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Re: Backfiring... carbs?
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Joined: Jan 2006
Posts: 7,694 Likes: 22
Monkey Butt
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Monkey Butt
Joined: Jan 2006
Posts: 7,694 Likes: 22 |
Removing the first 2 baffles really should not require any tweaking. Air fuel mixture screws maybe need to turn out 1 turn. The popping on decel generally means you are lean where the backfire on start shows a high concentration of gas. The symptoms appear to be opposed to one another.
don't twist the throttle when starting the bike that may be loading it up.
I try to aggravate one person a day. Today may be your day.
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Re: Backfiring... carbs?
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Joined: Aug 2006
Posts: 290
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Joined: Aug 2006
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Check to see if your airbox cracked with the "real loud backfire". You may have actually heard the airbox blow up as opposed to a simple backfire. That sound pretty much like what mine did. I had a large section on the top of the airbox break completely off.
Randy:
'05 TBA Green/silver AI out
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Re: Backfiring... carbs?
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Joined: May 2005
Posts: 34
Greenhorn
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Greenhorn
Joined: May 2005
Posts: 34 |
Chris, Just checking. Did you turn off the tank,fuel petcock when you parked? If not be sure to so gas won't build up when/where it shouldn't.I've read on site of "big bangs" occuring when this shutoff is forgotten.Be carefull.
cell phone to left ear gets swift kick in the rear(reebock to buttock)
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Re: Backfiring... carbs?
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Joined: May 2006
Posts: 1,025
Learned Hand
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Learned Hand
Joined: May 2006
Posts: 1,025 |
You can remove 2 baffels without any re-jeting. I believe you could even take out 3. Sounds like your mixture screw just needs adjusted. Here is a link to adjusting the mixture. http://www.bonnevilleamerica.com/forums/...mp;page=0#89123Scroll down to the Adjusting idle mixture (pilot) screws thread. 
06BA,-AI,NoBfls,K&NPods,TBS,155/45,2 3/4Out,SidGapPlgs,Wirsnbrs
NawImPrityFknFarFrmOkMan
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Re: Backfiring... carbs?
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Joined: Jan 2005
Posts: 1,204
Learned Hand
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Learned Hand
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BACK FIRING THROUGH CARBS-TOO RICH. BACK FIRING THROUGH PIPES-TOO LEAN......ANGELIS
Last edited by angelis745; 09/15/2006 6:39 PM.
1200CC BIG BORE, W/WISECO PISTONS,.250 STROKED CRANK, PORTED/POLISHED HEADS AND LARGER VALVES, CUSTOM WELDED EXHUAST, DUAL 42MM MIKUNI CARBS.
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Re: Backfiring... carbs?
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Joined: Jan 2006
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Quote:
BACK FIRING THROUGH CARBS-TOO RICH. BACK FIRING THROUGH PIPES-TOO LEAN......ANGELIS
I'm a little confused about this. I thought that the back fire through exhaust is due to being too rich?
This is because to fix the problem you un-screw the pilot screws allowing more air into mixture, which makes it leaner in my books....
TBA, Stainless extractors / drag pipes, 65mm over forward controls, Thruxton needles, 904cc, head ported, lowered 1-inch, Console removed, relocated battery box, Australia.
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Re: Backfiring... carbs?
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Joined: Apr 2006
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thats my impression also, the back through pipes means to much gas, if it was lean there would be no pop. but here i go again trying to think.
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Re: Backfiring... carbs?
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Joined: Mar 2005
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Leak in exhaust header = backfire. Turning mixture screws out = richer. Spitting back through cabs = lean condition. Exploding airbox = gas vapour accumulating in airbox being ignited by spitback. All separate issues - but related IFYKWIM.
Never whistle while you're ******....!
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Re: Backfiring... carbs?
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Joined: May 2006
Posts: 1,025
Learned Hand
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Learned Hand
Joined: May 2006
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High RPM's + closed throttle = less air "richer". (fuel can't all be burnt in cylinder)
Backfire in exhaust pipe due to high heat and accumulated fuel.
Make sense?
06BA,-AI,NoBfls,K&NPods,TBS,155/45,2 3/4Out,SidGapPlgs,Wirsnbrs
NawImPrityFknFarFrmOkMan
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Re: Backfiring... carbs?
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Joined: Jan 2006
Posts: 3,606 Likes: 2
Loquacious
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Loquacious
Joined: Jan 2006
Posts: 3,606 Likes: 2 |
Quote:
High RPM's + closed throttle = less air "richer". (fuel can't all be burnt in cylinder)
Backfire in exhaust pipe due to high heat and accumulated fuel.
Make sense?
High RPM and closed throtle means lean RPM of motor spinning causes a vacume thru the carb (think of it as a big pump)...more air...closed throtle and more air...means LEAN...and if you ever get rid of all the popping on a closed throtle decel...then your likely to be running to rich on closed throtle with low RPM...because you adjusted it a point that requires more air flow.
Lean causes uneven ignition and unburn fuel collects in the pipes, when it does fire hot gas ignites the gas in the pipes and you get pop-pop-pop on decel
THE VOICE OF REASON
per: Stewart
AF&AM/Shriner/Scoutmaster
130/45 TBS 2shim SS Uni 18/42
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Re: Backfiring... carbs?
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Joined: Jan 2006
Posts: 3,606 Likes: 2
Loquacious
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Loquacious
Joined: Jan 2006
Posts: 3,606 Likes: 2 |
Quote:
This is because to fix the problem you un-screw the pilot screws allowing more air into mixture, which makes it leaner in my books....
Normaly that would be true but due to the location of our "air screws" (engine side of carb NOT filter side) out actualy means MORE fule
THE VOICE OF REASON
per: Stewart
AF&AM/Shriner/Scoutmaster
130/45 TBS 2shim SS Uni 18/42
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