03 WR450 Bog on initial punch

I have read other suggestions, but still have problem.Im running 170m, 48pj, #40 leak, 2-1/4 turns out.pro circuit exhaust & they reshaped the head.I have tried many jetting combos. nothing seems to help.Problem only when you nail the throttle.generally at 1500-2000'

Have you done the BK mod? If not, do it. :cry:

Whats the BK mod?????

BK mod doesn't apply to to 03 or later models, YZ or WR...Yamaha changed the carb. See your manual about adjusting the accelerator pump...

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