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2007 crf250r popping back fire on acceleration

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Ok guys I recently got a 07250r it has all stock jets and carb has been cleaned multiple times it constantly back fires well revving I've been told its to lean but I pull the plug and its wet put my finger in exhaust and its black I've tried everything bigger /smaller jets timing not sucking air from anywhere starts and runs as soon as u touch throttle it back fires its ass off any help please thanks

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Not too lean. Just stop reving it and the popping will no longer be an issue.

You have a race bike, probably with an open muffler that has worn out packing. Not a trail bike with a massive muffler.

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strong spark weak spark strong spark weak spark strong spark weak spark, i think your hearing unburt fuel igniting after it builds up from missfires

Edited by goosey

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Ok guys I recently got a 07250r it has all stock jets and carb has been cleaned multiple times it constantly back fires well revving I've been told its to lean but I pull the plug and its wet put my finger in exhaust and its black I've tried everything bigger /smaller jets timing not sucking air from anywhere starts and runs as soon as u touch throttle it back fires its ass off any help please thanks

Have you ever

- checked the valve clearances

- re packed the silencer

- done a leak down test on the head

- clean all the wire harness connections, including the main ground wire

- cut back 3/8 off the plug lead and re-attach the cap

- tried a new plug

Edited by Krannie

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