Sounds like you have the Sportser engine. The old .40 was a great engine. The sportster was not as good, but works. They did make a washer that went under the head that made it run better. I don't remember much about what it was. Just remember putting one in and the engine worked better. You might find someone on here that knows about what that was. It was a long time ago. Good luck. You should be able to make it work.