Grinding noise started after engine installed

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6/7/2018 10:54 PM

Hey guys, I recently rebuilt a kx450f from the ground up, after I rebuilt the motor I turned it once or twice to make sure all was good and it sounded fine perfect. After I installed the engine back in the bike this grinding noise came up, sounds like it’s coming from the piston, I put new crank cases from Kawasaki, crank bearings/ countershaft bearings/ transmission bearings, All new seals, hot rods crank and rod, wiseco prolite piston, new timing chain, Hinson clutch cover on a stock clutch and a boyesen supercooler.

Just pulled the valve cover off halfway through typing this
And the noise stopped, put the valve cover back on and it came right back.

Weirdest thing ever, anyone heard of this before???


6/8/2018 1:15 AM

Ive never had fhis problem with my kx450. Since you localized it to the valve cover, my only guess would be an issue with that upper chain guide thats stuck to the inside of the cover. Is it pressed all the way on?


6/8/2018 6:15 AM

Aftermarket valve cover gasket too thin letting camchain rub cover? Do you have the dowels back in the camshaft holders? See what is rubbing cover to make noise.


Take it to the limit, one more time!

6/11/2018 11:29 AM

You should see if there is a spot thats rubbing on the inside of the valve cover. You would be surprised how certain parts will amplify a sound. Did you torque the cam cap bolts in the correct order and to the right torque specs?


7/6/2018 6:45 PM

Hey guys thanks for the help, I think it’s just noise from the cam lobes. I can send a video of it running but either way I’m going to send my head in for porting and polishing and new valves seats cut with new valves and new pro circuit can shafts. I’m planning on running a timbersled this winter so trying to get maximum power reliably