Crank gear key help......

Ok, bike started making a little noise Saturday while riding, so for giggles, I checked the valve clearance, needed to be done anyway. Then I pulled the clutch out to see if maybe the key and gear were loose, is there anyway to tell without taking the complete side cover off of the case? Or do I have to pull it all down and pull the gear off? The gear doesn't seem to move or have any play but it is not possible to see the ballancer(?) gear with the cover and other stuff still on. This motor was replaced last Sept. and I am thinking this is what happened to it the first time. What are the possibilities of Yamaha puting an '01 crank in it when they rebuilt it? As usual, thanks for any help given.

…is there anyway to tell without taking the complete side cover off of the case?

Not really. I suppose you could take off the mag cover and flywheel and check for play in the counter balancer shaft from that side…

The gear doesn't seem to move or have any play

IMO the only way to be sure is take off the side cover (not just the clutch cover) and see if there is any play in the counter balancer shaft. It should not rotate at all unless the crank moves also.

What are the possibilities of Yamaha puting an '01 crank in it when they rebuilt it?

You mean your dealer? I have no idea. See if they charged you for a counter balancer drive gear, because that would need to be changed also if they put a newer crank half in. It should be about a 30 minute job to find out for yourself (remove clutch and main gear).

Hope this helps.

You've got to pull the right side case to check the CB-key. Just pulling the clutch cover will tell you nothing. All the repair can be done by just pulling the right cover. I had to replace the right side of the crank after a failure. I'd recommend this to anyone who has to repair the cb-key more than three times. The gears begin to wear. The 2001 parts fit perfectly, and they are splined. When you repair the key, do a search first, but everyone who has repaired it has had better luck making thier own key and fitting it a bit long and tight. Make sure you tighten the nuts on those gears well and use a thread-locking compound. Good luck.


I second glens entire post.

I would doubt that the dealer would put the 01 parts in without a serious upcharge, or a specific request to do so.

If your key is going bad, its an easy fix really. Kind of expensive though, I think it cost me like 90 cents total. :)

One more question, I am down to the gears, everything is tight. Do I still need to buzz the crank nut off and look at the key and keyway or consider it tight from the feel of things?

Yep, I would. When you remove the cb-drive gear, look at the key. If there is any mark at all you should replace it. Mine barely had any wear on the keys that I replaced, but oooh the racket they produced. Remember, the torque force on that gear when you are wicking the throttle is way more than you could reproduce just by "feeling" for play in the gear. Hope this helps.


Thanks for the insight, I did pull the gear off and there are wear marks on the key. TT comes through again! Now, about this key, how do I go about finding the right size key stock and where? Is there a common size everyone has used or are they all different? I guess it depends on how much your gear is worn huh?

If you can find a decent industrial hardware store, if they dont carry it, you can order a piece of 5mm key stock. Dont bother with the Yamaha part. I think the created thier own alloy for the and some how counter acted the laws of nature and made a metal softer than lead for thier key :)

Anyway, get a piece of 5mm key stock, and make it as long as you can without it being longer than the gear is deep. Remember the broach on the crank tapers up to, so your key cant be in that area either. If your 5mm key doesnt want to fit, you can fit it by GENTLEY sanding it with 6oo wetordry sand paper on a piece of glass. You use the glass because its the flatest thing around, unless you have a surface block laying about or and end mill in your pocket. :D

Thank you very much guys.

I can only get them in packs of 5, 5mm square by 12 inches long. Anyone need any extra?

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