Are you speaking of 4 strokes?
I'm still wanting a China girl muffler that's got another six inches of pipe and/or muffler length-
I want less noise and the muffler not pointing the sound down onto the road where it echoes off loudly
I had a poo poo pipe on my 66 build for a couple of years- and definitely quieter, but I had to cut the pipe and recouple it with aluminum to make it fit-
and hanging it was always a problem otherwise-
They have some great things at Lowes CHEAP that look like the hangers with a long piece of angle iron on them too.
Some day I may try to braze the pipe and try it again- but I wish the standard muffler was longer and had more pipe.
I usually ride my 50cc bike because the 66 noise bothers me .