I had the same proplem with this motor, it would run at half throttle then die for some reason, then fire right up again first try. Hoping i have te problem fixed, i think it was sucking air at the needle valve intake. This was due to the refuling system that i was using pulling off slightly. I have adjusted and hope this will fix the problem. Does your motor do it at various needle settings and do you have a refuling valve?