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Yama426f

2002 yz426f video (EXTREME BACKFIRE)

7 posts in this topic

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!!!

http://www.youtube.com/watch?v=vIWb8TDZ5B0&feature=youtu.be

Edited by Yama426f

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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.

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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.

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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.

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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.

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

Edited by d3an182

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