YZ400F Cam Chain Sproket Question

Went to change the timing chain and sprocket looks like this. Looks pretty worn to me. Am I at panic stage needing crank replacement or if I change out the chain regularly can I milk this along for a while?


Anyone? :huh:

Hi ;)

I'm going to replace my cam chain too. Just got the magneto puller arrived. Gonna pull it off tomorrow. From what I was able to see through the cam chain canal in head/cylinder, my sprocket's teeth looked a little better than yours. It had grooves that fit the cam chain shape, but the teeth on sprocket are not cut on the edges (they are not rounded like yours).do. IMHO you're fine for a A WHILE, but you need to pay a lot of attention to it since its life is almost done. I'm not a mechanic but i think u could get some 20-30 more on it (with a risk of chain slippage if it will get worn more).


I'll post pictuers of mine sprocket tomorrow.


BTW I own 2004 yz450f that has lot of hours on it. Gonna start my own thread since I got couple of questions too.

Thanks for the input!


That is what I am looking for here in the post is just some thoughts. I know it's hard to tell but was thinking if there were some 400F experts out there that could share their experiences and point me in the right direction that would be great.

the quality is pretty low, but i promised to put it here :D


the teeth are really (you can cut yourself on it) sharp and the side edges are little bit cut,  just like yours are. i think it's living time is gonna end soon. all i'm gonna do is inspecting it every 20-30 hours. idk if it's necessery, but untill someone tells me it's not, im gonna do this, since i don't know !@#$ about it :).

check your chain guide.

crank sprocket1.jpg

crank sprocket2.jpg

Edited by sosycz

Thank you! I am in the same boat. No other responses so I guess I'll just run it and keep checking and changing the chain every 20-30 like you say and hope for the best! :thinking:

Your sprocket looks fairly well worn, personally I would start saving for a new crank, they run about $300 online...

Best I could do to help is offer my 0.02 and show you the pics of my old crank off my 2002 yz426 and the brand new crank I have yet to install. Sorry I couldn't get the greatest pic of the new crank cause of the bag but since I'm not ready to install it I didn't want to open it yet, but hopefully you can see how far off yours is from new it should give you an idea of how mch life is left.

ImageUploadedByThumper Talk1409077254.736121.jpgImageUploadedByThumper Talk1409077266.803094.jpgImageUploadedByThumper Talk1409077283.952634.jpgImageUploadedByThumper Talk1409077297.739262.jpgImageUploadedByThumper Talk1409077309.683430.jpg

The first two pics are of the old crank and the one in the sealed bag is the new one.

Hope this gives you an idea of the wear.

Thanks Spartan! That is helpful. Your old one really doesn't look that bad to me - compared to mine! Is that why you are putting in the new crank or other reason?


Also, where did you get the new crank? I was told these are pretty hard to get...

Sorry I never saw the notification to this response. I got mine from Honda east Toledo.com their shipping takes a little while... But it's free shipping with no tax and the best price I can find on the Internet.

It's not hard to find it's just expensive.

I'm replacing mine because my crank spun inside it's main crank bearings. The shaft wore away it's got a lip on it so it spins in the inner bearing race, I can slide it in and out of the bearing by hand

If I was in any doubt, I would aire on the side of caution and replace the crank. It may be expensive, but look at the other side? If your timing jumps a tooth, and a valve hits the piston, your looking at a butt ton of money for ALL new valves. Then gonna have to have seats cut. Valve guides replaced and lapped. Not to mention replacing a piston, and now your forces to replace the crank. Spend a little money, or spend a s*it ton. That's just my opinion.

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