Replace Chain ?

I think I know the answer to this question, but I'll ask it anyway. I noticed five broken teeth on my rear sprocket. All fresh breaks that I believe happened yesterday. The sprocket is a SunStar aluminum 51T, which is about two years old. The chain(O-Ring) has plenty of room for adjustment on it still and the counter shaft sprocket looks good. Do I need to replace my chain before I put my new sprocket on ?

I think you will be ok without replacing the chain, but if you don not mind spending the money, it would be a good idea since the rollers wil be strecthed out slightly on a used chain. If you do keep the chain, you should be ok. I have put 2 sprockets on my chain in 1 year and it still is wearing at the normal rate(pretty fast for these high horsepower beasts :) ) Good Luck


[This message has been edited by Matt406 (edited 05-21-2001).]

Call me Captain Anal, but I always replace the sprockets and chain as a set when the rear becomes overly hooked or the chain can be pulled slightly back and away from the rear sprocket (indicating that it has stretched).

A hooked sprocket will be thinner across the face, the smaller surface area can bend the pins that secure the rollers in the chain. What you will begin to see is kinks in the chain as the links don’t want to rotate back in a straight line due to the bent pins. If this gets severe enough you will run out of chain slack and break some things. Compare the thickness of the teeth ends on your old and whatever new sprocket you get and you will see what I mean.

Because of this I guess it is better to use an old chain on a new sprocket than the other way around, just make sure the chain isn’t beginning to kink up. I’d be surprised if it hasn’t given how incredibly long you’ve had it on there (or did you replace the chain more recently?).

I don’t know how often you ride but an aluminum sprocket only lasts me about ten or fifteen rides. I generally use Renthal sprockets and a Regina O-Ring chain.

I went ahead and ordered a new counter shaft sprocket and chain(had new rear sprocket already). I don't think Matt406 realized had long I had the chain on, about the same amount of time as the rear sprocket, I've learned my lesson. I compared the old to the new sprocket and noticed the teeth aren't hooked, but are extremely thin, I don't know how I missed this. I'm just glad I caught this when I did before any serious damage.

Thanks for the advice and information guys.

Dennis '99 YZ400F

I just replaced my chain and sprockets after a year of riding. My sprockets were very thin and hooked. The chain was doing the exact thing Hick described. It was not straightening out properly. That's how I knew I had to get the whole set. I never analyzed why this was happening, I just knew it wasn't good. (This list is great- I learn something new every day.) I also usually replace chain and sprockets together.

BTW, I'm trying out a Moose rear sprocket. It's extremely light and looks cool, too. It was $50.95 from Dennis Kirk, which I thought was a good deal. If anyone's interested, it's part number 8-466-49.

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