Hey folks, I tried to get on snowbum's site to answer this question, but all I got was an "Earthlink-This page is not found" page. AH! Anyway...I'm starting in on some maintenance prior to riding season and one of the things on the list is the front main seal (weepy, weepy). I'm planning to do the Enduralast kit anyway, so I figured while I was in there...replace the seal, etc. When does the timing chain usually need replacing on these bikes? Mine is a 76 r90/6 with ~35-45000 miles on it (bum odometer). I had some troubling vibration at the end of the season last year and I had a hell of a time setting the timing at the beginning of the season. I don't know if those are symptoms of the bike or my glaring stupidity regarding such matters. And, a bonus question: Does one need to remove the engine to do the timing chain as Clymer's instructs?