Listen at the carburetor and the tailpipe. It's possible you've got a burned valve or a carboned-up valve seat. Have you considered installing a slightly shorter belt instead of metal butchering?
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!