Hey Freedo, Those engines are not too hard to rebuild. Have to go down to the case and remove the jugs but if the body is good its worth it. Usually the number 3 cylinder is what goes out first being it gets the lease cooling. It also causes a popping sound, not a back fire sound. Sounds like in got overheated very badly and toasted the rings or ran it too low on oil. If you rebuild it, use Castrol 10-30 till brake in then go to either Texas Refinery 10-30 Pro Spec III or Amsoil 10-30. I use Texas Refinery in my Chevy 4x4 truck. It handles even diesel combustion temperatures, about 2 1/2 times that of a gas engine, and will help that engine last a very long time. I also use system 48 plus. Its no gimmick. Afetr nearly 41 years at turning a wrench, I'm very selective at what I put in my rigs. Its not Slick 50, which is ok for old engines, but something very different. I also used it in my diesel. Makes it spin faster in the morning and quicker revs and more power. Cuts oil temp down some also. Those 4 bangers need all the help you cab get. Especially air cooled engines. Regular motor oil just really isn't formulated good enough in my opinion for air cooled motors. I have owned a VW bug and know them quite well. Knew many including my brother that had them plus my friend who has an import parts store. He's rebuilt thousands of them over the years. I wish you well. Henry
