Everyone Should read this! (Cam chain troubles)

I know everyone that owns a YZ 450 has probably heard about this problem with the cam chain and/or cam chain adjuster by now. I was looking through past threads and found this problem multiple times! I personally have had this happen three times now, the last of which caused the shim bucket on top of one of the exhaust valves to break in half! This is an obvious problem that I think Yamaha should adress. I am sick and tired of having to rebuild engines because of a silly problem. I am going to write to Yamaha to address this problem which will not only cause a servre loss of return customers, but an increased liability as this is a saftey related issue, my engine locked in thrid gear through a whoop section this last time. If anyone has any info on a solution to this problem I would like to try it because I do prefer Yamaha for their performance and reliability. If there is no solution; however, and if the manufacterer will not even admit to a problem, I will have no problem trading my blue bike in for any other color!

Edited by Crawford43

What's the problem exactly? I have a hard time understanding how a cam chain or tensioner could have anything to do with a valve shim breaking.

...I mean bucket. Is the chain jumping on the timing?

I will have no problem trading my blue bike in for any other color!

I'm thinking going back to GREEN!!:thumbsup:

Camchains dont last forever if that is what you are saying is the problem. They should be replaced about every 40hrs or so. They are cheap anyways.

I'm thinking going back to GREEN!!:thumbsup:

I agree completely! What I think the problem is a faulty cam chain tensioner which lets slack in the chain allowing the cams to jump timing and "stick a valve", where the valve is actually contacting the piston and locking up the engine. Again this is the third time this has happened to my bike, and I had started checking the chain tension, changing oil frequently, and checking oil pressure with every oil change to prevent this failure. I just called Yamaha and they said there are no recalls on the producmost likely from lack of customers actually reporting the problem to Yamaha. I am going to write a letter to Yamaha and I suggest everyone who ones a YZ 450f and knows of this problem do the same. Letters can be sent to;

Yamaha Motor Corporation, USA

6555 Katella Avenue

Cypress, CA 96030

Edited by Crawford43

get a manual cam chain tensioner if you feel you have such issues with the auto chain tensioner.

get a manual cam chain tensioner if you feel you have such issues with the auto chain tensioner.

I just took the automatic tensioner off and it seems to funtion properly, but it was fully extended. So the chain must be wearing out and stretching, but it seems to stretch pretty quickly.

Ok. I've cooled down a little bit. I think I will just get a new chain and clean up anything that was damaged in the head. My question now is has anyone had more luck with a manual adjuster or should I just replace a chain more frequently?

If you take it off, it will automatically fully extend. That's what it's supposed to do. Any slack that develops is instantly taken up by advancing the plunger. The plunger can't be pushed back because you can't back a screw out by pushing on it.

wonder if something else is going on....i ride the dog piss out of my yz450f and checked the valves for the first time since i bought the bike, hadn't moved and the chain looked fine (replaced anyway) i'm guessing somewhere in the 200 hour range.

If you take it off, it will automatically fully extend. That's what it's supposed to do. Any slack that develops is instantly taken up by advancing the plunger. The plunger can't be pushed back because you can't back a screw out by pushing on it.

Yeah I know because its an automatic tensioner. To colapse it you have to turn the screw inside while pushing lightly on the end of the tensioner.

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