Backfire

I've got a 2003 BRP and when it's not warmed up all the way, it backfires, and it even does it after warmup (just not as much/dramatic) on the throttle braking. I've got a 172 and a 68, an applied smog block off, pro-circuit head pipe and silencer, hrc manifold, and a Uni filter. Why the hell does it pop so much? You'd think I was running 110 octane Turbo Blue or something that was exploding out of the bike's butt! :cry:

Try adjusting the fuel screw per the service manual or see this link for more info. It's free to try and it might help.

http://www.xr650r.us/xr650r_faq/#14A

Sounds like you've got an exhaust leak, check the tightness of the clamp where the header joins to the muffler and where the headers join to the cylinder head, while you're down there, check for black soot stains around the joins-sure signs of the joint leaking, which causes backfire. Failing that, give everything a good clean in the carby and make sure the airscrew is set correctly. Good luck! :cry:

Hows the valve adjustment,a tight valve lash will make it backfire :cry:

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