97 xr 600, has the "pop and die" problem as well. oh well... I'm not a racer or anything, but would love some more power; does the 628 kit provide noticeable power gains? also, need a new exhaust; what's the best on the market for performance? price? note: I love to hear my thumper, particularly on closed throttle... also, my chain picked up a rag and thrw itself off front sprocket, shattering engine case in front. temporarily repaired w/ "paste" and holding up well, but looking to replace. any ideas where to get cheap replacement and amount of labour involved? thanks guys.