I know we discussed this, but do you have the air box and expensive gasket in place? It won’t run at high speeds without these items properly installed. As a test, just to make sure we are on the right track, pull the primer out half way to the "warm up" position, when the motor wants to die out at half speed. If it now runs OK, we know it is lean for some reason. Get it to WOT with the primer in warm up, then push it back in, does the engine bog/stall out? If so, we don’t have a sync issue, we have a lean condition in the high speed circuit (including air box/gasket) for some reason….
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