Weird top-end noise. Sound clip inside...

[Masterphil]

UPDATE: Weird top-end noise. 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 left side (sprocket side) of the exhaust cam, or best I can tell. 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?


http://www.dirtrider.net/gallery/misc.php?do=downloadfile&i=1313

 

[Masterphil]

OK, It sounded like cam chain slap to me now that I think about it a little bit more. I remember reading a "How-To" adjust a manual cam chain tensioniser and remember the article mentioning that you should let the bike idle and loosen the tensioner until it sounds like a glass jar full of marbles. That's exactly what this sounds like.

Now i deed to search to find out if someone makes a manual cam chain tensioniser, or how hard it'll be for me to fab up one.

 

[Masterphil]

Well, I took off my tensioner and there is nothing wrong with it. It's not the tensioner. The cams are timed correctly and the clearance is in spec. I have no idea what it could be now.

 

[YZ165]

Are the Cam Chain Guides all A-Ok? That's the only thing I can think of. That, or your Yamaha just dosen't want to be thrown to the wolves at a KTM Dealership. ;)

 

[Masterphil]

...or your Yamaha just dosen't want to be thrown to the wolves at a KTM Dealership. ;)

I think that's it! Seriously, though, I really don't know what this could be. There is no loss of performance as a result of the noise and the noise dissappears if I rev it a little.

 

[YZ165]

:think: Sounds like it's time to tear it down. :(

 

[Masterphil]

Pulled both the stator side cover and the clutch side cover. Nothing loose, broken or with excessive play. Pulled the cam cover, both cams are in time. Nothing broken, loose, the cams have no side to side play. This sucks!

 

[Masterphil]

http://www.dirtrider.net/gallery/files/5/5/2/3/4/426EnginePieces.JPG

Well, I bit the bullet and tore it down tonight. It's the left side main bearing. While I'm in here, I'm going to replace both main bearings, the cam chain, tensioner, and the crank if it's out of spec. I'm not really sure what happened to the bearing, but it was on it's way out. I'm just glad I tore it down before it took out the cases/crank and the entire top end.

 

[Masterphil]

My parts came in today, a new cam chain, tensioner, some lockwashers, and new main bearings. Pressed out the old bearings and pressed in the new ones. I used the good old freeze the crank and heat the bearing trick to install the crank into the left main bearing, works like a charm. About an hour ago I got the engine installed back into the bike and fired it up… Perfect. Smoother sounding than ever. The knock is gone. Squeezing that engine in there was a PITA! Time to take it out for a beating.

 

[ScottS]

Good Job !