95 KDX200 missing at high speed

[JMR1977]

I have a 95 200 that has less than 10 hours on a fresh top end. It has a boyesen rad valve and LA sleeve with Wiseco piston. 1st 2 rides went great (no problems). Rode the 3rd time today and had a bad high speed miss after warming up. Will run fine on a fresh plug for about 5 mins or so. Was doing same thing prior to rebuild, just felt that it was due to scored piston. Overall hours on this bike are very low. Top end was done during repairs to trans (gear seized on counter shaft). Bike seems to be jetted ok. Could this be an ignition problem? Help greatly appreciated.

JMR1977

 

[G. Gearloose]

Tighten all grounds and check for corrosion.

In my dictionary jetted ok = crap.
jetted right = hold on holy crap this is great!

If jetting and airbox are original then its likely running rich and fouling.