(1) Compression test
(2) Ignition test
(3) Fuel delivery
(4) Carburetor
In (2) if the points/condenser were replaced with electronics, was the generator also replaced? Electronics DEMAND a stable voltage! Using electronics with a generator is like playing with a molting rattlesnake!
Probably not (3) as no issues under load
In (4) if you are forced to use fuel with ethanol, the carburetor MAY be lean due to the reduced energy content of the ethanol. When under load, the metering rod is pulled up in the jet to the power (richer) step.
IF YOU ARE ABSOLUTELY POSITIVE 1, 2, and 3 are not an issue; try increasing the diameter of the main metering jet by 0.001.
Jon.
