engine popping

[logg3rhead]

I have an 06 yfz450 and I was just wondering what causes a motor to pop when you let off the throttle while riding. It only pops once when i give it gas sitting still but does it more when theres engine brake slowing down. I replaced the piston with a wiseco 12.4:1 and have 15 hours on it. It didnt start popping till now, after some hard riding. please let me know

[GPracer2500]

Make sure your exhaust header gasket is good. An air leak there will cause decel popping. Also, a lean pilot circuit can cause decel popping. If you're sure the exhaust gasket is good try backing out your pilot screw (aka fuel screw) in 1/4 turn increments and see if that relieves the condition. If you need to go more than about 3 turns out (from fully seated) then go up on your pilot jet and adjust the the fuel screw again.

Bear in mind that minor popping on decel is not abnormal for most carbs. The high vacuum created under closed throttle decel creates a temporary lean condition. It's just a fundamental deficiency in the way carbs work.

[250r4life]

like GP said...

i was lean in my low to mid range and my bike would do the same. it would run like a champ when i was racing the hill at the dunes, but when i was coasting back to the bottom it would pop quite a bit... i put on the accelerator pump and went up on my pilot, and that took care of it.

[logg3rhead]

Thanks a million guys, its always great to get intelligent feedback. Ill try it all out and see what happens.