Rear Sprocket Bolt Clarification

[itsatoy]

So I got a new set of lock tab washers and started to torque down the sprocket bolts to 47 ft lbs and the first one snapped off. I got it out but now I'm a little confused. Forum search is giving me a range of answers.

For the torque I only have one setting listed in my manual for "drive sprocket" "22mm nut" 47.0 ft lbs. I'm guessing thats the wrong one since it says its a nut. On the forum I have seen I think 27, 47, or 80 ft lbs. I don't know which is correct for an '81 XS650SH.

I have seen lengths of 25, 30, 35mm. I think maybe I need m10 x 25mm x 1.25 pitch?

Finally, with all the horror stories of these backing out, I see recommendations for lock tight, some recommendations against the stock safety tabs, and even safety wire. Whats a newb to do??

 

[5twins]

You're using the wrong torque spec for starters. That 47 figure is for the big nut on the front sprocket. And it's wrong too. Yamaha, for some reason, has changed that front sprocket nut torque spec many times. You'll find it listed for some years as low as 36 and others as high as 90. Accepted practice is the use the higher value. It seals the sprocket better and makes it less likely to leak oil.

The rear sprocket bolts are speced at 22 ft/lbs. Use anti-seize or the bolts can seize into the wheel. I use the stock lock tabs. I think the length varied over the years between 25 and 30mm. Check what's in there now and just get the same length. Yes, M10 x 1.25 pitch sounds correct. They are a fine thread but for M10 bolts there are 3 thread pitches available. There's the standard or "coarse" pitch (1.5), this 1.25, and an even finer one (1.0). These are the middle pitch available.

 

[itsatoy]

5twins to the rescue. Thanks again!

 

[Johnnyb89x]

What is the bolt property class of the rear sprocket bolts? would an 5.8 suffice. It seems to have the range for that specified torque value of 22 ft/lbs.

 

[5twins]

I would use something stronger. Even though the torque on them isn't super high, they are subjected to lots of side load and shear.