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Yamaha - 03 660 Suddent Engine Noise

Yamaha YFM660R Raptor (2001-2005) - Yamaha ATV Forum - www.bluetraxx.com
New to the forum!

I bought a 2003 660 Raptor late last year. It is in VERY VERY nice condition, very low hours. The only issue it had was some minor blue smoke on start up, which I diagnosed as valve seals. I tore the engine down (I am very meticulous) and replaced the valve seals and 3 valves (the valves seemed a little worn, lapped new ones in). While I was in their I measured the stock piston and cylinder.. both were well within spec. So for good measures I just installed some new rings. I put everything back together and also installed a Stage I hotcam. The smoke disappeared (like I expected) and the motor purred like a kitten (and ran like a raped ape).

Other mods include full exhaust (new) and dynojet kit with airbox mod.

Fast forward about 30-45 mins of riding (gentle riding) and all of a sudden I get motor noise. It went from dead quiet to a knocking sound in 2 seconds. The sound goes up/down with revs. It's hard to pinpoint the source.. sometimes it sounds like top end (valves) and other times it sounds like mid/bottom end. It's not too deep, not to high pitched either. The cam chain and tensioner were well within spec and it great shape (less than 1/2 out).

Bike runs great but is now noisy. Again, it went from quiet.. to instant and constant noise. I'm a little puzzled on what could of happened so quickly and under such gentle riding that now makes it knock. One a scale of 1-10, 10 being about to explode and 1 being slight valve noise.. I'd say it's about a 5. Certainly doesn't sound great.

Thoughts?

Thanks
Date: May 24, 2017    Labels: Yamaha


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