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03 660 Suddent Engine Noise

5K views 5 replies 4 participants last post by  cory52000 
#1 ·
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
 
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#2 ·
Did you double check the operation of the decompression mechanism? If assembled wrong it will make noise. You will want to pop the rocker cover off and double check to make sure the bolt on the de-compression setup are not coming loose. It will ruin your rocker cover if it comes loose.
 
#3 ·
I saw you said you got a hot cam put into it, are the valves seated to the stock spec or the hot cam spec? I put a hot cam into mine and when I seated the valves to stock spec I started getting a loud knock coming from the upper end of the motor followed by it stalling out, I reseated them slightly larger of a gap and the knock went away for me, figured that maybe this might help you as well.
 
#4 ·
Decompression mechanism is not loose. Popped off cover everything looks great and timed. Cam chain tensioner is less than 1/2 way out. When I put the hot cam in, I set to hot cam specs. It ticked a little so I called hot cam and they told me to adjust a little tighter (factory specs). It went away and motor was dead silent. Dead silent one second, knocking the next!
 
#5 ·
Ok, so I've got it torn down. Cam chain tensioner and chain well within spec (less than 1/2 out). Piston, rings, cylinder all within spec and great looking. Valvetrain looks great.. absolutely NO play in crank and wrist pin. I can't see anything engine-wise that would cause this. I've got a buddy that came over (a lot of engine experience) and we are struggling to see what could be causing this issue? Obviously something changed instantly, but we can't find a smoking gun!!
 
#6 ·
i assume the noise matches engine speed no matter the gear. did clutch in or out make a difference. sounds like you have methodically ruled out everything inside the engine. if i was you i would pull the stator cover and look for something loose in the stator flywheel or starter clutch. the only other thing i can think of is oil pump
 
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