2002 yz426f video (EXTREME BACKFIRE)

Well I just got a new to me 426.. I noticed that it backfires alot.And tends to bog when I get on the gas. I think the exhaust is missing a connecting piece, I can see fire coming out the pipe What do you think can cause this??((SHowed in VID) I read around and played with the idle screw which stopped it a lil, but not much..I plan on cleaning the carb and maybe a re jet if needed cause it does have an aftermarket exhaust.. White Bros if im not mistaken.Check out the video I made though and give me some feedback. THANKS!!!


Edited by Yama426f

Backfire on decel. The first thing I would do is to clean out the exhust, repack anything in the silencer, and see what happens. I plug one end, fillit up with low odor mineral spirits, and shake well while also tapping the pipe(s) with a deadblow hammer. This usually does the trick, especially if I plug it off and fill the pipe up. Usually this will clean out any deposits if soaked overnight. While doing this I would also make sure your timing is dead on as well. Maybe a valve slightly out due to cam or cam chain that is causes a retardation. In my experience, it is usually the pipe needing cleaned. I hope that helps some.

If you have a visible exhaust leak, it is likely that that all by itself is most, if not all, of the cause of your backfiring. Get a new seal for the mid pipe joint from Yamaha and see how it works after that.

Thanks MArshall.. I'll give that a try. And Gray that is what i thought it could be because you can clearly see the flame coming from the mid pipe but was not sure.

My buddies 426 started doing the same thing. It was like lean popping really bad. Checked valves, exhaust leaks, jets in carb. Come to find out the air adjustment screw/knob on the bottom of the carb feel out.

Uugh, you need a clamp around the midpipe to start.

Thats just a bad connection between pipes causing an air leak and maybe a very rich mixture

Edited by d3an182

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