quote BillW:
I would take a close look at the throttle cam follower adjustment. Your carb throttle plate might be opening a bit too soon in relation to timing advance. 18s like to wear out the cam follower roller. This makes it so sometimes it’s adjusted right and other times, it’s not, based on the random clock position of the follower roller. Also take into account the wear in the linkage. The throttle plate itself should JUST be about to open when the roller lines up with the mark on the mag’s throttle cam.
Bill makes an excellent point here. I have also had cam followers that were bent slightly and would not allow the throttle plate to fully open, even with the cam adjusted out. Where you have had multiple powerheads swapped around, you may have run into this as well. Worth looking into.
You are learning a lot about these 22 cube motors. I had a 1959 Fastwin that was the best running motor I ever had. The fiberglass cowl rattled a bit at slow speed, but that motor ran the best of many. The separate Hi and Low speed adjustment is miles ahead of a fixed jet motor.
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