Knocking noise when on high revs

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Hi guys.i need some advice before moving to the next step.when bike is idling theres no noise but when reving the bike up to 8000 rpm it starts making a knocking noise but on top in the motor.though it was bearings but its not a screech sound.

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Hmmm

So - it this a progressive noise, does it get louder as revs increase ?
Is it every bang of the engine or is every second bang .... ? If it's a camshaft related thing it will be at half time to the engine.
Could it be a misfire ? - at 8000 rpm youre going from idle to main jets so it could be this .... have a look on ebay and get a mechanics stethoscope put the end on the engine so you can hear whats going on inside. listen to each of the 4 cylinders through the block and on the exhaust so you have a better idea of where the sound is - Note I don't know how loud this is going to be so be careful. Listen to the cam cover

If you think its a misfire - look at the choke and make sure it's disengaging all the carbs, are the carb rubbers (where they join to the engine stubs) split or cracked ?? then check the airbox is on the carbs again check the rubbers and the see if the air filter is clean.

When did you last change the spark plugs ??? Have you worked on the bike recently ???

It gets louder when reving up.another guy from a bike shop told me its the crank thats worn out.and now the piston is touching the head.could this be true?

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It could be ... to honest without hearing it or taking it apart I can't really tell.

If your engine was toast what would you want to do ? Cut your losses and buy another bike or look for a 600 engine for a transplant ???

Evilchicken0 wrote:get a mechanics stethoscope

Big Screwdriver....