Your research is what solved this one, Paul, rather than our suggestions. Before sending my last post I wondered if anyone had been inside the crankcase, read your posts again, and decided nobody had, which meant the centrifugal governor was not a suspect. Your phone call discovered that the engine had been in the hands of a lout, which meant all logical back-tracking on history was useless. I wonder if he did any other harm inside the crankcase? Like removing the piston and rod, and reinstalling them backwards, or with half a pound of grit in the big-end bearing? Frankly, in that situation I'd be tearing everything down and checking it out in some detail. It's already a miracle if he got the camshaft timing right.
