1996 yamaha wr250 motor knocking?

[3wheeler80]

I just picked this bike up last night. It runs great starts right ip and cant keep thebfront end down. But left side by clutch cover it sounds like someone is kicking like when i am cruising around and in a low rpm and i give it throttle it starts making that popping/ tapping noise. Loud i can hear it over the motor. But the bike runs great. I just changed the oil and it was veru dirty(dark black/gray) i was told its the crank bearings? Just dont want to keep riding it if it is somethong mayjor. Any help would be appreciated thank you

[HuffieVA]

Its likely if it was crank bearings the port timing would be off and not run or start great, its still a possibility, but since you say it runs good it may be piston slap to much space between the piston and cylinder from wear or over honing making a tapping sound) either one is not good, if you ride it with a bad crank it will eventually come apart, if you keep slapping the piston it will eventually break into pieces and likely drop to the bottom and ruin your crank, or tear the cylinder up. The best thing you can do is pull the head and investigate.

[3wheeler80]

Thanks for the reply. Well the noise comes from were the clutch is.

[HuffieVA]

loose bolt at one of the clutch springs hitting the inside of the case? Bent main shaft (I rebuilt a blaster that had one)

[3wheeler80]

Yeah possibly. But it only does it at low rpms. Could it be my front sprocket being worn and popping?

[just ben]

Thanks for the reply. Well the noise comes from were the clutch is.the problem with that is you said it comes from the left side... the clutch is on the right side

[3wheeler80]

no my clutch is on the left. and i dont think it is the motor knocking . i think its just the clutch going out or yeah something in there is loose or broke. (my clutch hops a lot, like a car)

[3wheeler80]

My fault it is on the right. It does it the whole time. Idling and through every gear. I dont want to tear it down as ive never tore into a motor

[just ben]

so is the noise from the left or the clutch side? A stethascope will pin point it (I think harbor freight even has them) in a pinch a 2' length of a broom stick will work.

[3wheeler80]

i traded it off. it was the lower crank bearings and i didnt want to split the cases