Differential Torque

[yamaha1300rider]

Much has been written about not needing to torque the engine drain bolt as much as stated in the service manual. However, I do not recall an explanation of why the standard torque settings for the engine drain bolt and the rear drive drain bolt are so different - like a factor of 2!

Now the bolts are interchangeable??

Is the answer to do with the different metals into which they are tightened? If so, why does the rear bolt not leak at its recommended setting whereas the engine bolt would presumably at the same setting?

Does it also follow that the engine drain bolt could be tightened to the spec of the rear bolt and not leak??

Your thoughts and answers, gentlemen

Paul

01 fjr

uk

 

[radman]

Ignore the recommended torque specs unless stripping drain plugs is on your list of fun things. They do fine just set at "snug". In fact, reduce most if not all torque specs by 10%, unless doing drivetrain internals.

 

[shuswaper]

I agree with Rad., forget the torque specs. on this one ...and, use crush washers and go by feel. Pssst...it`s not a differential (nor can it be, with only one wheel involved). :assasin:

 

[yamaha1300rider]

Thanks guys - I would still like to know why Yam suggested the 2 dissimilar settings.

Shuswaper - I know it does not have a differential - I said "differential torque" as in "difference in 2 torques"

Paul

01 fjr

uk

 

[sparky3008]

Thanks guys - I would still like to know why Yam suggested the 2 dissimilar settings.
Shuswaper - I know it does not have a differential - I said "differential torque" as in "difference in 2 torques"

Paul

01 fjr

uk

Why do they send it without much of it greased properly.

Why are some of the bolts so tight no one can get them off without an air gun and the torque setting spec is 17 (hand tight).

If you ask why Yamaha does anything you will just go :wacko:

 

[Geezer]

Just a guess here, but I would say that there is a lot more pressure in the crankcase than there is in the secondary drive. With the pistons popping up and down there is a vacuum and pressure effect that is more likely to let the oil work past a loosely threaded drain plug.

OK, that said, I'm sure there are others here who can give a better explaination.

The reality is that the drain plug does not need to be very tight in order to not leak. And, per Radman's recommendation, you do not need to use a replaceable crush washer, a copper washer works just fine and does not need to be replaced at each oil change.

 

[Centerline]

Just a guess here, but I would say that there is a lot more pressure in the crankcase than there is in the secondary drive. With the pistons popping up and down there is a vacuum and pressure effect that is more likely to let the oil work past a loosely threaded drain plug.
OK, that said, I'm sure there are others here who can give a better explaination.

The reality is that the drain plug does not need to be very tight in order to not leak. And, per Radman's recommendation, you do not need to use a replaceable crush washer, a copper washer works just fine and does not need to be replaced at each oil change.

+1

And the crankcase metals are going to be operating much hotter than the rear end.

 

[charismaticmegafauna]

I'm not so quick to judge Mama Yama -- they probably have a reason.... I'll go out on a limb and suggest that there may be considerably fewer threads in the crankcase than in the final drive housing (I haven't looked....)? But, as I've had a machinist try to explain to me on numerous occasions, tightening torque is akin to "stretching" the threads and that full torque can be applied if thread depth is, at least, 1/2 the diameter of the fastener. That being said, I've become a believer that one must develope a "feel" for such things -- failing that, it may be a good idea to use smaller size wrenches (in general) for all but the largest fasteners.