ASK THE MXPERTS: Why Does My 2006 Yamaha YZ450F Pop At Low rpm and Refuse To Start? Is There A Jetting Fix?

Dear MXA,   
   My 2006 YZ450F pops at low rpm, when decelerating with the throttle off and it doesn’t want to idle. Also, it won’t start without choke even when warm. Have you guys experienced something similar with this model?

   Your problem is not uncommon on the 2006 YZ450F and the fix is relatively simple. The standard pilot is 42. We have had luck fixing this problem with a 45, 48 or 50 pilot jet. The choice depends on how severe the problem is (you be the judge). We would start with a 45, since summer is coming, but run a 48 pilot in cold weather.

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