Motorcycle Repair: sparkplug blow-by, honda 350, heli coil

Question
Hello, have a 73 honda 350, bought as a parts bike few years back, now trying to restore, have bike running but someone cross-threaded one of the spark plugs,it threads(it appears) all the way in but as it runs I'm getting a small amount of blow-by around plug..It runs surprisingly well but would like to try to fix problem..Is there something I can put on threads, like pipe tape for plumbing or a liquid sealer of some kind...mike

Answer
i usually only answer questions on harleys, but I think I can help. The only thing youa are going to be able to do is pull the head, drill it out and install a heli-coil. There is really nothing else that is going to work.
Good luck and happy riding
Mike