i got 60,000 miles on mine and havn't touched it except for maint. i know alot of people with over 100,000 miles and haven't rebuilt yet.if you can find out how it's been maintained that would be a start. i don't know what a dyno test would prove that a compresion test and a general test drive couldn't tell you but maybe i'm wacked. sheet, i know people with 100,000 miles on a drive belt.