Final drive swap

[BA80]

Yes, I understand that is what y'all ar speaking of. However, the pinion and ring gear WEIGH much more than 4 lbs, inch or otherwise and the laws of physics say that it will take a force greater than the mass of any given object to move it, let alone overcome the resistance of the 4 roller bearings it all rides on.

Do you realise how little force 4 in. lbs is?

[DGXSER]

it really is very simple, read the book. HERE is a link to it.

[James England]

However, the pinion and ring gear WEIGH much more than 4 lbs, inch or otherwise and the laws of physics say that it will take a force greater than the mass of any given object to move it, let alone overcome the resistance of the 4 roller bearings it all rides on.

Do you realise how little force 4 in. lbs is?

I dont think that's correct. It's possible to move a ten ton weight using a 12v motor from an electric drill, if the gearing is right. That's how worm drives, or pinions or gears work things. In the case of the FD, it's not moving 4 pounds in weight, it's rotating it via gearing. It's completely different.... is it?

[BA80]

Well James, that pinion is not geared down.

It has to be moved/rotated and in turn overcome the resistance of two roller bearings and the resistance of the teeth meshing to rotate the ring gear which has to overcome the resistance of two more roller bearings and the mass of the carrier to rotate the carrier. At which point inertia takes over.

[DGXSER]

The same physics that defines torque is what allows the 4 " pounds to move that force. Bending moments or commonly known as leverage.

[Dudenatz]

3Phase: Thanks for the correction. I do have a type II, so 3.4 - 4.3 in. lbs it is. I clicked the link recently posted, and I have rarely gone wrong by following the manual written by the nice folks who make the things I work on. FWIW, I have an inch-pound screwdriver with a range of 0-36 in lbs. It is a click-type that I use to torque screws on carburetors, to keep from warping them. I'm pretty sure they come cheap on eBay, but I could be wrong. I think in this instance a beam-type would be the correct application, because rolling torque is usually less that break-away torque, or the effort required to get the thing spinning, not maintaining the spin.
BTW, you guys are great. A simple input gets me a list of available torque tools for my application, as well as many different takes on one particular situation. Anyway, i'll get the input set up, then start stripping the silver paint on my way to an MNS re-do.

[cywelchjr]

Greg, grab hold of a pinion, I've got one sitting in my garage, so I know you must have at least one out there, and turn that thing (use a good one not a FUBAR one), the one I've got doesn't take anywhere near 4 lbs of force to turn it, it take very little actually, and that's my original FD, which the only thing wrong with it is that the seal at the wheel connection (I forget what it's called) is leaking which is why I did the mod.

It's one thing to say that it should be set with heavier preload than 4 inch/lbs but to say that you can't get it that low is just incorrect and seem to imply you haven't tried it? Cause while I believe the shaft drive manual to be correct with it's spec for preload, it's just not correct that you CAN'T get a 4 inch/lb preload, you CAN get it so it takes that little effort to turn the input shaft, and my stock FD is right about there (by calibrated hand torque wrench ) and certainly nowhere near 4 ft/lbs. And my 750 FD which was untouched before I modified it was certainly nowhere near 4 ft/lbs of preload either. I did it so it was just about the same turning force after I made the changes as it was before I did, which was pretty close I think to 4 inch/lbs.

[BA80]

You brainiacs sure are a lot of fun to mess with. I still think 4 inch lbs is a little on the light side though.

[cywelchjr]

You brainiacs sure are a lot of fun to mess with. I still think 4 inch lbs is a little on the light side though.

That's cause you Okies don't read manuals. It's in the book, and the book is good, it's a good book, I've got it.

[BA80]

I think 15 or 20 is a more realistic number. IMHO

Just from experience.

[cywelchjr]

I think 15 or 20 is a more realistic number. IMHO

Just from experience.

I'm not sure how that would affect bearing life. I'm pretty sure that the Yamaha engineers did some pretty complex calculations to determine the right number for proper bearing life. You should be able to get 100k out of them without abuse, so only 30k isn't quite there, and if you hotrod it then all bets are off anyways since the 750 FD's are not as heavily built as the 11 FD, so doing a lot of wheelies and such is likely not a good idea. But, we will see, since you have that many so far.

[BA80]

and if you hotrod it then all bets are off anyways since the 750 FD's are not as heavily built as the 11 FD, so doing a lot of wheelies and such is likely not a good idea. But, we will see, since you have that many so far.

Is there any other way to ride a motorcycle?

My FD is out of a 1980 850.

[crazy steve]

Figuring bearing preload is a bit of a black art, but what surprises me is the fact that Yamaha makes no allowance for whether or not the seal and/or bearing are new. I know that the times I've worked on automotive differentials that the pinion preload number would be different if you were working with used parts vs new.

And the 'low' preload numbers given for the XS FD are in line; a Ford 9" rear has fairly high preload on the pinion with new parts (22-32 in-lbs), but that drops to 8-14 with used. These numbers are for much larger bearings/seal too. Going too tight will kill the bearings, and in pretty short order too... DAMHIK..

[3Phase]

Dude, if you have an in-pound screwdriver that would work fine. Get an adapter and set the screwdriver to 3 in-pounds. Turn it slowly and when the pinion is tight enough to make it click you're there. The main thing is not to overtighten the bearings so a little loose is better than too tight and don't pay that obstreperous Okie any mind, he always gives the nuts and bolts in his engines a couple of extra yard-pounds of torque when they start to get noisy 'cause it's easier than changing the bearings.

Do you realise how little force 4 in. lbs is?

Of course not, Greg. Why, I've never used a torque wrench before so of course the first thing I'd do is use it to see how much the parts weigh instead of how much force is required to turn them. Thanks!

By the way, how would you set the bearing preload in a differential that weighs over a ton? Foot-pounds seem like they would be way too small and the scales on most common torque wrenches don't go over a couple of hundred of them at the most anyway so there must be some trick to it!