98 YZ Carb problems

Bike ran fine (stock-including carb settings) throttle sticked so cleaned carb and put back together. Afterwards, wouldn't idle, misses/backfires from 0-1/4 throttle. Is very lean in this range. Cleaned pilot jet,(even went richer one jet) tried richer on air screw, nothing. Cleaned carb many times still nothing. Bike runs fine 0-1/4 with choke out. Any ideas on why the difference after cleaning carb. Thanks for any input.

two thoughts: One-your carb has a fuel screw, not an air screw. It's adjusted oposite from an air screw. Apologies if you already know that.

two-double check carb connecting points on both sides. You may have an air leak somewhere.


I have a '99 400 and one day, after running perfectly, out of the blue, it starts doing the same exact thing. I took it all apart and found my fuel petcock seal was deteriorating and pieces were contaminating the carb. Any contaminants can clog a jet. The popping represents a lean condition which is why it runs fine with the choke on. Also any air leakage between the carb and head will cause this condition. Do a search on this site re: lean carb as alot of research has been done already and I'm sure you'll find some quick fixes.

Good Luck


Lez Ride!


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