One of the biggest problems with the twins when not starting is the rings. Just check to see if there is some kind of compression.Just put your finger over the spark plug holes and see if it has compression. I guess you have already checked to see that it has spark? Also which model twin is it? As the later models had electronic ignition on them. Could be a faulty ignition as well,but let's check compression first. They shouldn't have much as when they run,they have more compression than at starting point. Let me know how you get on.
