A bike that old may have a magneto ignition or points. Do you know? Have you looked in an online shop manual? Like wow... thou dost proceed from ignorance. Take the whole ignition system apart, clean all of the connections INCLUDING THE GROUNDS, check the coil / mag windings for continuity, check the spark plug for continuity, look up the words you don't know, and replace the bad stuff. I would put in a new plug and plug wire on general principles, but that's me wanting to maintain it in good condition.