I realize that some of the problems may be from my inexperience with gas engines. However I have built at least 20 RC planes (most kits, not ARFs) and never had this much trouble with any plane. The problem with the muffler it that the threads in the engine head are TOO SOFT. The bolt would go in EASILY 2-3 complete turns before it became difficult to thread and by that point the mounting hole was cross threaded. Within 5 minutes of trying to bolt on the muffler, both holes were cross threaded and I was in trouble.

I may not be a gas engine expert, but I can install two bolts.

In retrospect, I should have stopped at that point and tapped the holes. I managed to get through the difficult things - a very obscure engine/throttle/choke install. I got the cannister muffler in, and when it came time to just install two little bolts I ran into big trouble.

Leonard