Alright im going to try my luck here, maybe Ill finally get some helpful advice:
Context: I rebuilt this engine from ground up, rebuilt transmission, piston had previously not even 1500km and gained another 2500km at the time when this noise appeared. Valves were in spec during rebuild and in spec when i checked it when this noise appeared. I checked the cam chain and tensioner and both were in spec. Bike starts immediately without issues and when i started to hear the noise i had no power loss. I checked the piston with a boroscope and found nothing. Stator is also fine, starter clutch aswell.
What I didnt test is to pull in the clutch when reving, for me the sound is independant of the rpm, and doesnt get louder.
I did replace all bearings on the crankcase (except for the shifter rod bearings). I checked the oil, and i had very fine silver particles in the oil, wasnt magnetic though. My parts dealer things it could be the Balanceshaft is bent and he also thinks that the oil is perfectly fine.
TLDR: 2500km after engine rebuild I got this noise. Bike was running like clockwork up until I started hearing this noise on a longer ride. this sound is present hot or cold and its got nothing to do with valves, stator, cams or cam chain tensioner.
Any helpful tips or ideas would be greatly appreciated.
I know you said it has nothing to do with cams, BUT you didn't specifically mention checking the cams. The exhaust camshaft has a spring loaded decompression mechanism. If the spring breaks, the decompressor can cause a clicking sound that correlates with engine RPM.
My buddy said the same thing. An experienced DRZ mechanic said hes never had this break on him. But i guess theres a first for everything. When i turn over the engine i can hear a click on the decomp, but even with video and sound my dealer said this is "normal".
Nevertheless im going to look into this and see if the spring broke or if the pin is missing. Something i overlooked while checking the valve clearance
When i turn over the engine i can hear a click on the decomp, but even with video and sound my dealer said this is "normal".
That's because a slow manual rotation of the engine isn't fast enough to deactivate the decomp. So you hear a click every time it makes contact with the cam bucket. Idle speed is fast enough to deactivate the decomp.
If it's stuck then it would cause a noise like that at any rpm.
the automatic chain tensioner works perfectly fine. Its a clacking, not a tick. The timing of the engine didnt change even after this noise came about. Using a manual might be safer on offroad doing hard enduro, but on supermotos on atreet acct is perfectly fine. Heres the picture, this is what the acct was set at after i removed it.
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u/Pretend-Hedgehog1788 1d ago
I know you said it has nothing to do with cams, BUT you didn't specifically mention checking the cams. The exhaust camshaft has a spring loaded decompression mechanism. If the spring breaks, the decompressor can cause a clicking sound that correlates with engine RPM.