Rear sprocket bolts

Originally Posted by yorkie_chris

You checked with yam or are they hilariously expensive?

I phoned J&S Accessories today (my nearest Yam dealer) and they could not check the price or order anything in because it was bank holiday, and they are now closed until Wednesday. I'll phone another dealer in Tamworth tomorrow, I don't like the idea of asking an acessories shop for mechanical parts anyway, at least with a dealer with a workshop you have some chance of getting the right part and the right advice.

TBH I don't like the OEM design and prefer a bolt, the threaded rod is a pain, you undo one and you get the nut off, you undo the next one and the rod turns with the nut and you get the whole thing, why not just use a bolt?

Specialone, thanks, I'll call you at some point tomorrow.

[yorkie_chris]

Because a bolt moves with respect to the thread as you apply torque increasing risk of tearing metal. Especially with cheesium yammy alloy.

Stud, threads are stationary, you apply torque to nut so apply direct tensile force to metal of threads rather than combined tensile/surface traction (or frictional shear or whatever you want to call it)

Originally Posted by yorkie_chris

Because a bolt moves with respect to the thread as you apply torque increasing risk of tearing metal. Especially with cheesium yammy alloy.

Stud, threads are stationary, you apply torque to nut so apply direct tensile force to metal of threads rather than combined tensile/surface traction (or frictional shear or whatever you want to call it)

OK, so less risk of stripping a thread, and if you do strip a thread, it's the nut end, not the sprocket carrier end.

OK so long as there is a good reason for the extra hassle, and given how little I trust my cheapo torque wrench (ok for 25nm, ok for 100nm, but at around 60nm I'm sure sometimes it just decides not to click and way overtightens) I'll get some OEM Yamaha ones ordered.

Originally Posted by yorkie_chris

Sids reasoning for using shouldered studs was more valid than my in that case

The OEM studs are shouldered where they meet the sprocket. Given that I stripped the threads below the nuts, and had to get a pair of mole grips on those shoulders to get the stud out, am I correct to conclude that I should use studs, or would I actually be better to find a Hi-tensile shouldered bolt?

My difficulty with finding a bolt is that the shoulder length tends to be too long, it has to be 12mm or less, or the bolt is going to stop turning before the sprocket is held on tight.

[yorkie_chris]

Are the threads right to the surface of the carrier?

Originally Posted by yorkie_chris

Are the threads right to the surface of the carrier?

No they are recessed by about 6mm, and the shoulder on the OEM stud is about 6mm, so I figure 12mm on a shouldered bolt is actually too long. I need to find something at more like 10mm or less.

[yorkie_chris]

Yes that sounds right. Not sure where you'd get those if local engineering place doesn't have them.

Maybe they would have studs with a plain shank in middle.

Originally Posted by yorkie_chris

Yes that sounds right. Not sure where you'd get those if local engineering place doesn't have them.

Maybe they would have studs with a plain shank in middle.

I think ordering OEM studs from a dealer is going to be easier than trying to find a suitable bolt, and they must be fit for purpose.

[yorkie_chris]

Yup. Some yammy spares are actually not bad prices. Bits for my RD400 were cheap enough

Originally Posted by yorkie_chris

Yup. Some yammy spares are actually not bad prices. Bits for my RD400 were cheap enough

Yeah, they do have that reputation on Horizons Unlimited. Not in this case unfortunately

22 quid for the four studs, bolts and the lock tabs. They should be available to pick up on Friday.