03 YZ Camchain damage

I posted back about 2 months ago when my 03 let go. Three intake valve hit the piston and wreaked a bit of havok on my motor. Many of you where very hepful as to try to find the root of my problem. I have had the project on hold becuase I was building a workshop out back and because the snow in Ontario limits my want to ride. Anyways I have found the problem.

My camchain was the sole problem and it cost me over $1000 in repairs. Up until this point I didn`t realize the camchain would stretch that fast, but obviously I was wrong. It streched so bad that it shaved an 1/8" of aluminium from the cases up to the head from slop! It also chewed the sprocket on the crank half (part of the crank, not pressed on) so bad that that is why the chian skipped.

I would love to show you guys some pictures of the damage so you could prevent it, but I dont know how to upload a photo to this board.

I suggest that everybody take out there camchain tensioner and let it come out all the way. Then place it back in to see how much of the tensioner adjustment is left. Trust me, once to tensioner has no more to go, the chain just starts desroying things in it path. Oh yeah my guides were toast as well.

good warning thanks for the post.

sorry to hear this.

i have been preaching frequent cam chain replacement for 2 years now.

Many riders on the drz forum have gone to a mechanical tensioner.Seems that on rapid deseleration that the tensioner does not recover fast enough to pick up the slack cousing the chain to slip.I don"t know if this was the couse of your problem.Just a thought.

I too am sorry to here this!

i have been preaching frequent cam chain replacement for 2 years now.

I also have an 03 YZ250F. How often should I be checking this? I am a casual rider (mx/sx) I don't race or anything like that and can't afford for this to happen. Is this a big deal to check and change the chain? Is there a better chain and tensioner out there?

Thanks

the manual covers this.

i like the once a year change approach unless you are a pro or desert racer.

stock is fine if you keep it new.

I'd still like to bump mx26's question about whether or not there is a stronger cam chain/tensioner available? If they are subject to failure, wouldn't it be cool to have an extra tough one? I am no expert at all, not a great mechanic, but from my dumbass perspective, this does sound desirable.

has anyone swapped their cam chain and/or tensioner for a different (stronger) one?

thanks much

I would love to show you guys some pictures of the damage so you could prevent it, but I dont know how to upload a photo to this board.

raleydog,

if you email me your pictures, i'll create an index and post a link to them. use jds-net@losdos.dyndns.org and email me a ZIP file of all your pics.

regards,

jim aka the wrooster

'01 wr250f

Thanks I will send the pics right away.

My local shop suggested the idea of removing the camchain tensioner (very simple) and letting the spring unwind all the way (maximum adjustment). Then you push it back in the hole (while it is still all the way out)until it takes up the slack of the chain. If the tensioner does not go in all the way... your ok. This is because your are not using up all of you tensioner. Im sure you get the idea. This also gives you a starting point so you can keep an eye on it every month or so. You can bet I will checking my tensioner every month!

what we need to do is find somebody that will make the tensioner body out of delrin. Then we can use a much stiffer spring in it without fear of premature wear. Otherwise the chains gonna eat the tensioner.

But using a spring driven tensioner is the way to go, unless you want to add tightening the cam chain to your religion.

It"s my understanding that most cam chain stretching should occur in the fisrt 500 to 700 miles of usage.At that point you realy shouldn"t need to adj. it very often.I have a Hayabusa tensioner on the way for my drz.Seems a little safer.Just my.02 cents

sndmn2, The chain is like all other chains. While there may be a higher rate of stretch at first. It will continue to stretch.

Consider the drive chain supplied with the bike. It never stops, and it's rate of stretch is huge always. They may not have put much better of chain inside the bike either.

Just my 2 cents, but it sounds like the tensioner was simply not working correctly. The idea of checking the tensioner as part of your new bikes "preventive maintence" seems like a MUCH better idea to me than putting a different part in there that may inadvertantly do the same thing by applying too much of too little pressure on the cam chain and sprokets than the stock tensioner. If the tensioner is working correctly and not at the end limits of the range, there should not be a problem. I feel strongly that checking the timing chain is something that we should do often although it is easy to forget coming from 2 strokes. On any interference 4stroke motor, we have to remember the importance of this simple part that is vital to the survival of our powerplant and place importance on it as part of the 4 stroke PM regimine....

:)

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