check and see if the bronze(brass?) caps on the bottom of the carbs has been removed. if not, remove them carefully and depending on your elevation adjust each one a full turn ccw. this should aleviate the popping. as far as the deal you got, i think its awesome, the guy probably ran the fuck out of it but if he put new rings in he may have bored it over slighlty so you actually have a faster than stock bike now. i got an 02 with 2750 miles and 5 year warranty for 3000. i put 1000 into it and its just about finished, only thing is a couple of scratches on the left faring and left tail.