I need help. Sound clip inside.

I took my 02 426F into my local KTM dealer to see what they would give me for a trade-in. He looked over the bike and had me start it. I kiked it over (once) and it fired right up.

It's sitting there idling like it always does and he says to me:

"That dosen't sound good"

"That's going to have to be fixed before we can take it"

"That's really bad"

I just say that it has always sounded like this, or at least I think it has always sounded like this...

I have linked to a sound clip that pretty accuritely represents the "bad noise" that is coming from the engine. This bike has a high comp piston and a 450F auto-decompressor camshaft for what it's worth. Does this just sound like normal YZF clatter? or is something wrong with my bike?


Your link went bad in the copy-paste.

Yes, there is something wrong with that motor.

So far this is what I've done:

Pulled the cam cover - Cams are in time, clearance is in spec. No parts missing or broken. Cams have no side to side play.

Pulled the Stator cover - Bottom cam chain sprocket is good. Nothing loose or broken. The balancer has no excessive play.

Pulled the right side engine cover - Checked the bolts with lockwashers, goodntight they are. The clutch basket is good, no excessive play.

Pulled the tensioner - It is extending fully without retracting, as it should.

I am at a loss. I have no idea what it could be. I have searched and checked all of the things that other's have had problems with. When I drained the oil, It looked normal, no shavings or discoloration. It only makes that sound at idle or just above idle. If I rev it, It dosent make the sound anymore. There is no apperant loss of power, and it runs fine. Any ideas as to what it could be?

Check to see if the noise stops when you pull in the clutch, or with the bike idling in gear.

It sounds like gear rattle, which would be normal for the most part. The engine does not idle at a steady speed, but accelerates each time it fires. This acceleration yanks the slack out of the transmission, slamming the driving faces of all the gears together. Then, the engine comes up against the next compression stroke and loses 2-400 rpm very quickly, racking all the gears against their coast side faces. Then it fires again, and so on. The result is a growling/rattling noise.

It's hard to tell from a recorded clip, but if the noise stops when you rev the engine and returns as it settles back to idle, goes away when the clutch is disengaged (pulled in) or placed in gear, and the bike makes no growling noises underway and shifts OK, it's probably normal gear rattle.

I don't think It's normal gear rattle. The bike shifts fine, but it does make the sound if the clutch is pulled in wether it is in gear or not. The weird thing about the noise is that it isint constant. I mean it isint consistant with how loud it is or with how often it happens. Don't get me wrong, It's always doing it, but there is no steady beat to the noise like there would be if it was a valve hitting a piston, etc. That's why I keep coming back to the timing chain/tensioner every time I think about it. It's the only thing that I can think of that would be causing this kind of noise. At least I hope the problem is as simple as a new cam chain/tensioner.

Does anyone have any experience with the APE manual cam chain tensioner or with any other aftermarket tensioner?

Have you checked for loose balancer shaft bearings?

Here's an update. The noise does not go away when I rev it like I originally said it did. The noise is still there, it's just harder to hear. I pulled the clutch side cover again today, the main gear, counterbalancer gear and clutch basket nuts were all very tight. There isint any slop in the counterbalencer or bearings for the CB. I'm just about ready to say **** it and ride the thing. But the last thing that I want is to really do some damage.

Could it be your cam chain banging around? That is what I would suspect.

My first post so take it easy on me :applause:

Any clue why I can't access that sound clip, would like to hear it for comparison to my bike and what I'm hearing. Just purchased an 01 426 and want to be sure I won't be having a major headache anytime soon. My bike runs great, just a comparison for normal 4 stroke noise and what may be problematic would be nice.


Try checking your clutch basket to see if the basket has wear notches on the basket teeth. The notches could cause your clutch to rattle. The clutch basket teeth should all be smooth.

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