FactoryHondaMx Posted November 4, 2015 I recently bought a 2007 crf250r and it runs great other then when I let off the throttle it backfires very excessively. I don't know if this is normal or if there is a problem. (It had dual pipes by the way) Thanks. Share this post Link to post Share on other sites
Excitable My Rides (6) Posted November 4, 2015 start by checking the valves and the timing. Share this post Link to post Share on other sites
CRFRida1605 Posted November 4, 2015 Verify your pilot jet is the right size and make sure you dont have a leak in the exhaust either at the head or where the header ends and the y pipe starts to the mufflers. Share this post Link to post Share on other sites
FactoryHondaMx Posted November 4, 2015 Thanks a lot guys I'll look into both of your suggestions. Share this post Link to post Share on other sites
418Stroker Posted November 4, 2015 Turn fuel screw out 1/4 of a turn. Share this post Link to post Share on other sites
nzgsr Posted November 4, 2015 (edited) Sounds like lean pop, caused by an exhaust leak or a lean pilot circuit. To richen the pilot circuit open the fuel scew 1/4 turn and retest. Edited November 4, 2015 by nzgsr Share this post Link to post Share on other sites
