1971 idle twice as high when hot
 

One kick fires right up,idle goes way high when hot. Any ideas?

also any ideas on where to get a free flowing cigar muffler for this beast?
Had the quite stuffed up original on it, got an aftermarket one that was better ,but turned colors in a day.

carb nice and clean? right jet and no air leaks? something i would check..

Sounds like an intake leak going lean on you .

Intake leak like the man said as the motor heats up stuff moves and it sounds like your intake is sucking air .. my pan did it alot till I got the right combo of rubber o rings and aircraft clamps ..no more prob