Breaking up on the top end

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what has been described sounds too rich on hi needle, squeeze the hi speed down find the peak again

if its the stock carb (?) that maybe all you're gonna get and won't matter what you do.

could be a fuel flow problem, filter, screen... esp. after leaning it out a bit.

heres it from DDM....

If your engine stutters at full throttle and cannot reach full RPMs:

The high jet is too far open. Close the jet by turning it clockwise slightly, and then ride-test. If no improvement, repeat until desired results are achieved. Once you have found a workable setting, open the jet approx 1/16 of a turn to ensure sufficient fuel/air mix.
 
i see its WT 990, still too rich if winds up and breaks up at the top end.

and the differential would be fuel flow after that , being the wind up is solid.
 
Last edited by a moderator:
I ended up ordering a vstack and filer last night. I'll reset the coil gap, new filter, new plug, and try again. Lean it a 1/16 if it's not better. I'll try and snap a video next week when I get it back out.

Thanks for the recommendations.
 
Anyone actually measure their coil gap? How much run out are you seeing? Setting with the motor at TDC to .35mm (.13 thousands) the it gets as tight as .004 at bdc. Is this normal in these? Seems like a lot of run out.
 
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