We are fairly new to the race scene, my son is racing a 2002 kx65 and I'm wondering if it's time for a top end rebuild. He started racing late in the 02 season, the bike has very little practice time on it, mostly just race day riding. The specs given on compression are 157, his checks at 140 (wot 10 or twelve kicks on a cold engine). How useful is compression test as far as determining the need for rebuild? What are all of your thoughts?, is it time, and if not at what point would you suggest. Any advice would be appreciated.