First thing I would check would be the timing . Sounds like it is restarted as stated above. Try to advance the timing by turning the dizzy counter clockwise about 1/2 in. and see if that helps. If that's not it check your advance weights in the dizzy and make sure there not stuck, then check the carb. It's kinda hard to tell without more info. Like what kinda dizzy( mechanical or vaccum advance).