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Discussion Starter #1
I need help, run out of ideas.
Engine starts to knock suddenly. It's knock at idle below 2000-2500rpm. Sounds really bad and I've got no idea what is this.
Was replaced the piston because of slack and clutch basket buching (it has grooved a little). Was checked connecting rod and crankshaft its good. All was checked under both covers and all looks fine too.
I have a video, maybe someone can give an idvise what can it be.
https://www.youtube.com/watch?v=aOiC3ddjPa8
 

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Hard to say - how much extra vibration is there ?

get a mechanic's stethoscope
it will help you pinpoint where noise is from -
they work good and are cheap -
 

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I was going to say crankshaft - big end bearing but if you've checked the crank already then it's really only bearings that can have gone. Main bearing? In any case. You're going to need to split the cases and go in I think. It will be obvious once you're in there.
 

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Discussion Starter #4
Extra vibration just a little.
Try to use wrench as a stethoscope and as I think it can be still crankshaft or something around that.
Maybe was some mistake about crankshaft.
Going to take it to service at thursday and they disassemble all engine.
Hope they find a reason.
 

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It won't be hard to fix. These engine's are simple. I've got a Husky 610 and a KTM625 and I've rebuilt both of them in the last year. It strikes me that big singles are the same almost, inside the cases. You have top end, crank stuff, bearings and gearbox. Throw in a little clutch, some oil pumps and some timing stuff for the valves , some ignition and electrics and that's really all there is to it. It's a case of going in and looking. So yes... It's all fixable. It just takes a bit of time. So don't stress. If your rattle came on suddenly, then I'm betting a bearing let go. Try not to ride it too much in case you've got debris floating around in there from the bust part.

Oh... Just had a thought. How tight is your cam chain? Might want to take a look at your tensioner and make sure it's still tensioning.
 

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Discussion Starter #6
Yesterday got checked tensioner. Its been only 5 clicks on it and its holding tight in there.
 

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How did you check con rod low end?? Sound says it is it.
Main bearings can be checked very easily, open the small one cap on to the left side cover. Put the rod between cover and end of the crank axle. Try to push up a bit crank axle, if bearings are bad you will feel free play and notice it visually.
 

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Discussion Starter #8
About cranckshaft is ok was told me by serviceman. He said about it "in the first look its looks ok" because of was found problem with piston and he decided it was it.
 
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