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Maintenance mistake: improperly staked countershaft sprocket nut


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When I replaced my drive set recently, I got a surprise when I removed the cover over the countershaft/front sprocket. The staked nut that holds the sprocket secure on the countershaft was loose.


Talking about this part

90179-22018-00 c/s sprocket nut, pinned

This OEM nut has a "lip" 360 degrees around it, and the countershaft has two "staking" cutouts on its circumference. A properly installed c/s nut is torqued to 70 ft lbs and staked on two sides 180 degrees opposite each other.

Last time I changed out drive set, I used a new 90179-22018-00 countershaft nut, and I rubbed a light bit of engine oil on the threads (the c/s threads seemed to have small amount of corrosion visible). Torqued to 70 ft lbs (holding the foot break).

I had the right size punch tip, and I struck the punch cleanly with good force, and the first cutout was well staked.

I was so satisfied with my stake job, I skipped staking the second cutout. And that is the mistake. It worked itself loose and I have been riding it for some time that way.

Properly stake this c/s nut every time you put one on

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Kind of a shame Yamaha didn't use a simple large diameter washer with the appropriate ID design to fit the countershaft splines, so they could simply fold the OD of the washer up on the nut to stop it from backing off.   So many motorcycles have used this simple technique over the years that it just makes sense.   Might have to look into having one cut when I change out my CS sprocket.   

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