# Backfiring through exhaust



## zacksbf (Sep 11, 2009)

Ok, my brute is having issues. I thought my tuning/jetting was off a little because before it would backfire through the carbs some at idle and part throttle. I worked on it til I figured I needed outside help. I took the brute to CATVOS and bought a HMF slip-on from them and gave them my stage one jet kit to do a re-tune. They installed the pipe and jetted the brute and the jetting/tuning is good now. Problem is it now backfires through the exhaust at idle. Once I give it some gas it clears right up and the power is amazing so its not affecting that part of it. CATVOS tried the same things I did when it was poping thru the carbs. They exchanged the Dyna with the stock CDI and it didn't help so they tried the coils from another brute to see if it was those and it didn't help. The plugs are good. Obviously its not a restriction in the exhaust so what would cause this? The choke moves freely also.
The brute started doing this after it sat for about 8 months and I ran seafoam through it and it has had a couple of tanks of fuel ran threw it since then.


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## NMKawierider (Apr 11, 2009)

And the valves...they are all set correctly? Have you taken a compression test on both cylinders to see if there is any real difference? Has anyone taken a gas analyzer to see where all the levels are at different RPMs? Notice any leakage around the pipe flange areas? Might have a leaking exhaust gasket.


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## RDs Neighbor (Jun 24, 2009)

Try adjusting the fuel air mixture screw on both carbs. Go an 1/8 turn in, and then an 1/8 turn out, and see which way is better, and then continue in that direction until it clears up. 

I would try that first.


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## phreebsd (Dec 16, 2004)

that's what i would do as well. A/f mixture.


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## zacksbf (Sep 11, 2009)

I will try the A/F settings and see if it clears up and let everyone know what I find. The valves have not been adjusted yet so I will plan on doing that after mudstock. I was orginally concerned about it being the valves but because it clears up sometimes and then comes back it doesn't seem to be a valve problem.


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