Hi all i have just put a new zdz 50 in my aircraft and i don't know if it's a tuning problem but the motor takes a bit to clear after the first start, then it;s fine with the transition but a funny thing happens from about 3/4 throttle to full throttle i drop revs. there is no problem with the servo geometry so i guess it is a tuning problem, any help would be appreciated

Cheers Dale

If there's no throttle stop the carb could go past wide open....Maybe too rich on the high speed needle...

sounds like someone removed the throttle stops --- the throttle plate is going past center position.

isn't the throttle stop on the high end part of the craby case it self?

the arm that came on the throttle hit a high/low stop - It is easy to remove this when adapting another arm - and the common result is that the throtle plate now will turn over in the bore . So getting the throttle plate to stop horizontally in the bore becomes a setup of the servo linkage .
worse yet - often, the plate is rotating the wrong direction - and the engine runs badly -hard starting - no midrange etc..

I have not changed the linkage arm but i have removed it and put it back on, i can't get a good look down the bore while the motor is in the plane. the stop that i was thinking about is the one on the otherside of the carby, the one where there is the idle stop is.

Thanks for your help

It seems that the top end was a little lean, the problem seems to be better, not sure if is the correct fix, does this sound like a symptom of a lean top end?