Excessive popping on deceleration? (Video)

Go up two sizes on your pilot jet. Yamaha 4s are notorious for running lean. I would bet a good amount of money that it's the pilot.

Don't want to sound like a smart A#$ but, have you cleaned your air filter lately? My KLR650 was popping all the time and I chased it about then one day, a month or two after a dusty Gorman, CA weekend, I checked it out and oh my GAWD!!! There it was! Cleaned it in solvent (UNI), oiled and now the beast is perfect with NO POPPING!

Just one of those basics I missed and I'm an Aircraft / Rocket Mechanic!:eek:

Go up two sizes on your pilot jet. Yamaha 4s are notorious for running lean. I would bet a good amount of money that it's the pilot.

Bad advice.

Do not arbitrarily change jetting. There is a method to determine the correct pilot jet and fuel screw setting (already posted in this thread). The old wives tale about "all bikes are jetted lean" is total BS. Bikes are generally jetted for sea level, 68 degree, 30 inches mercury and 50% humidity.

Race bikes like a YZ are designed to be raced. Not putted about. Racers do not coast. If you want to coast, you run a well muffled WR woods bike with the ACV functioning.

Bad advice.

Do not arbitrarily change jetting. There is a method to determine the correct pilot jet and fuel screw setting (already posted in this thread). The old wives tale about "all bikes are jetted lean" is total BS. Bikes are generally jetted for sea level, 68 degree, 30 inches mercury and 50% humidity.

Race bikes like a YZ are designed to be raced. Not putted about. Racers do not coast. If you want to coast, you run a well muffled WR woods bike with the ACV functioning.

Um my method was derived from not only owning/racing Yamaha YZ/WR's, I also worked as a technician at Yamaha for years. Did things like factory trackside support at the MX races and road racing venues...so yeah like you said, horrible advice.

Thanks for all the advice, as there is a lot of different advice I think I'll take it to either my local mx shop or my local dyno tuning place as it looks like it will be beyond my present skills!

Bad advice.

Do not arbitrarily change jetting. There is a method to determine the correct pilot jet and fuel screw setting (already posted in this thread). The old wives tale about "all bikes are jetted lean" is total BS. Bikes are generally jetted for sea level, 68 degree, 30 inches mercury and 50% humidity.

Race bikes like a YZ are designed to be raced. Not putted about. Racers do not coast. If you want to coast, you run a well muffled WR woods bike with the ACV functioning.

...and thanks for the WR advice, I'll remember that as I ride my WR supermoto in to work today.

Thanks for all the advice, as there is a lot of different advice I think I'll take it to either my local mx shop or my local dyno tuning place as it looks like it will be beyond my present skills!

I would go two up on the pilot and see if that helps. It's relatively easy to access and you will save a lot of money if it helps. If not, you're only out a couple of dollars and a few minutes of time.

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