Today I checked the possible root causes suggested in this forum: reversed plug wires 2&3 and ignition timing. Both were fine. I notice an additional symptom: when the engine e is in forward and toped-out at 1500 rpm, the rpm is not stable but varies slowly up and down by approximately 200 rpm. I would really appreciate some advice.
My A4 will not accelerate beyond 1200 rpm when in forward. Acceleration in neutral and reverse is fine (> 2000 rpm). I replaced the whole carburetor with a new one from Moyer and this had absolutely no effect on the problem. The prop is clean. I don't know what to do at this point.