Does is backfire or afterfire? Afterfire is in the exhaust a backfire is through the carbs. You could be running rich, does she crank up fast from a cold start? Like, a little too fast? Do you see smoke or smell somthing not right? Do your plugs look really dark and carboned up? If you answered yes to any of those issues think carburetor if your answered no think timing advance is stuck in the higher range, or back to carburetor your high speed jets may be dumping fuel like your floats are bad or some odd,
so lets start at how does she start?
