Muffler keeps blowin' gaskets.???

[Nomad]

My muffler keeps blowing gaskets for some reason, I decided to bash the muffler with a hammer to make clearance from the lower mounting studs ( I know it's not the right way to do it) I will not "Rube Goldberg" any more mufflers or other parts, Modify; yes---- bash with hammers NO... anyway I have cut the muffler off the pipe and installed a shorter muffler (small eng muffler from Ace hdwe) worked ok and acutally made the eng quieter but the exhaust "note" was a little more "piercing"... decided to install the original muffler via copper spacer and there's no tension on the pipe but it blew the gasket after a few minutes, during which time the engine actually ran better .. smoother, more power.. can anyone tell me where to get a muffler/pipe setup that I won't have to "fiddle" with?... I'm gettin' tired of this *&^($#@ muffler issue...

[Bikeguy Joe]

You may want to use a file and make sure your flange on the header pipe is nice and flat.
Do the same to the jug after you remove the studs.

[Venice Motor Bikes]

It could also be clogged up w/ rust or ??? & have too much back pressure...