It sounds like it's lean or has late ignition timing. Try advancing the timing a few degrees, and also check for vacuum leaks. Run an unlit Propane torch around the intake and carburetor base gaskets to see if it's sucking air anywhere except right down the carburetor throat. How does it respond with the choke knob pulled partway out?
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!