check for a weak spark, if it has 1, then get a condensor for the points system, they are a good culprit with weak sparking, and cheap, also, a ign system requires more voltage/ spark at higher rpm's, which could count for the sputtering also, and theres a chance that because the condensor was going bad, it compleatly went dead and that is why it won't start. if the spark is fine, look in to the fuel system as your problem, carb and fuel pump mainly.