I did a piston a month or so ago and the machine shop said the from the looks of the piston it looked like it was running a tad to the lean side. Should I move the needle of buy a lager main jet (one size larger)? The piston was 7 years old when I rebuilt it so it was runing dangerously lean.
Also, how do you tell if the belt is worn and ready for changing without tearing the case off and looking?

 

If it was just a 'tad' lean, and you don't go wide open all the time, just raising the needle one notch should do it. Also make sure your air screw is set properly, too.

 

If it ran for 7 years without blowing up, I'd say your jetting is perfect! Don't touch anything unless you want to sacrifice performance.