RE: How to keep muffler bolts tight
here's a thought. Thermal expansion of two different metals, aluminum/steel.this is what works for me because of the difference.
Clean the threads on the cyl. head, same for the bolts. alcohol or similar, use green or red loc-tite, put the muffler on snug the screws, run the engine ttill its good and warm/hot then finish tightening the screws. also the can,if pitts style muffler must have a support bracket to the firewall.