XS750 Final Drive Swap

[gareth]

Started to install the XS750 final drive and now have a couple of questions.
I cleaned up the new drive and temporarily fitted it to the wheel so that I could remove the retaining nut. It came off VERY easily, which surprised me since the tech tips suggested an impact wrench. Anyway, I have been very careful not to move the position of the drive since I took the nut and spacer washer off. In the meantime, I filled up the oil holes with high-temp silicone and cut and ground a thin fender washer to seal both holes up. Its setting up now.. I did not pull the gear mechanism from the housing.

My question is..

Should I grind off the thickness of the fender washer from the spacer washer in order to keep the total thickness below the nut the same?? The spacer washer is about 4mm thick in this drive

And what is the torque that I should apply to the retaining nut when I tighten it all back up again? I did a couple of searches on this and the links that I found to the "final drive specs" .pdf manuals are no longer working.

There was some note in one of the posts about this being torqued to about 4 inch-pounds or so, which feels loose, although the nut was easy to get off..

I just want to confirm this before I do something stupid that could easily be avoided by having the right info...

Regards,

Gareth.

[DGXSER]

[QUOTE=gareth;286910] Should I grind off the thickness of the fender washer from the spacer washer in order to keep the total thickness below the nut the same?? The spacer washer is about 4mm thick in this drive

Nope, not necessary. Actually, depending on which version of the 750 FD you have it may not even be a spacer washer. If your drive has the phillips head screw in the end plate that mates to the swing arm, it is a type II and has a crush sleeve inside the FD that sets the spacing.

And what is the torque that I should apply to the retaining nut when I tighten it all back up again? I did a couple of searches on this and the links that I found to the "final drive specs" .pdf manuals are no longer working.

It is supposed to be 3-5 ft-lbs of torque to rotate the drive when it is properly tightened. The spec says somethign like 75 ft-lbs on that nut, but I can tell you form experience, if you use half that the drive will not turn like it should. So just tighten the nut until the drive just barely starts to get resistance from turning.

[gareth]

Cool, quick reply, Thanks..
It does have the single phillips in the end casting, so I am going to assume it's the type 11.
I will button it up at the suggested torque and move on.
Having a bit of trouble getting the drive shaft out though. Thought that just pulling it with vicegrips was supposed to do the job, but its a slippery little sucker..

Thanks again,

Gareth.

[DGXSER]

No problem....BTDT Printed up the T-shirt....

The way I found to get the drive shaft out fairly easily is to take a piece of wire...like the white or black piece out of #12 romex and wrap it around the bell shape of the drive shaft. Twist it a couple times so it won't slip off, then grab it with the Vicegrips. Then hit the vicegrips with a mallet to drive it out.
carefull, it will try to fly across the floor.

Now putting it back in, that is another trick. I take the rubber boot loose on the driveshaft side and get my finger in there to hold the sleeve the drive shaft slips into at the right angle and rotation. Even then, it is a bit of trial and error to get it in. Those are the most complicates parts of the mod though.

[gareth]

Got the shaft out. I think it hangs up on the small spring clip at the end of the splined shaft; I left that clip out when I was putting it back. Putting the shaft back was pretty much a carbon copy of DXser's method. I shone a flashlight down the swingarm and then tried to hold the UJ in just the right position while sliding the driveshaft in with my right hand. Looked a bit like I was playing the worlds largest, stupidest 2-button accordian on my knees, but no one was looking.
I made the spacer from a piece of chrome plated tubing that I had lying around. It was a bit loose and I used a piece of tape and some RTV to hold it on. I'm still not 100% sure that I have the retaining nut at the right torque, because it was done more by "feel" than anything else.
But it went together eventually. I used the original spring from the 750 drive. The xs1100 spring seemed to be a bit too long and to apply more pressure than I had noticed when I took the original drive off.

Everything turns. Going to let it dry overnight and take it for a test tomorrow.

[MindWebs]

i think you are told to use the 1100 spring in the instructions.

fender washer??

just use a 1/2 inch washer and leave out the original washer that's in there.

did you read the instructions at all??


whatever works, i don't think it's the end of the world.
run it a few miles and check temp to make sure all is well.

Happy riding!

[DGXSER]

The first one I did I freaked out on the torque of that nut as well. As I adequately displayed in an earlier post, I am a bit anal about torquing stuff. So it kept me up at night thinking I did not torque it right, but even half or so of the spec torque and the thing would not spin hardly. So I got advice form members here, some looong time members that I know have done MANY with alot of miles on them. That was when I learned about the crush sleeve. So, as long as you torqued it up decently a touch over hand tight or so, and the FD did not give you much resistance to rotating on the wheel, all is good.

I took the one off of Thunderstruck a few weeks back and found the copper sleeve I put in had basically no wear at all to it. Really, the driveshaft, the sleeve/spacer and the U-joint all turn together so nothing is rubbing against anything. It is basically a static piece, just turning as an assembly pretty quick.

As to the spring, if you can see the end of the driveshaft at the end of the U-joint piece it slides into, then the spring is doing all it should.

[gareth]

think you are told to use the 1100 spring in the instructions.

fender washer??

just use a 1/2 inch washer and leave out the original washer that's in there.

The purpose of the washer was merely to seal the oil holes off. I chose the thinnest washer that I felt could do the job. 'bout a mil thick, etc. My next concern was how this extra thickness affected the overall length of the driveshaft and if it made a difference.
Try to remember that this is a modification.
And question all " instructions"...
Most of this stuff is a work in progress..

It never hurts to ask..

Oh, and watch "Gran Torino"..

There's a line in there about orders not followed...

[petejw]

i was only talking about his the other day,
when we used to replace diff seals i would center
punch the nut and the shaft, so when replacing you
could torque up the nut and allign it with the shaft,
if you were to put the washer in to block the lube
holes you could grind the thickness off the nut from the
thickness of the washer and retorque the nut back to
its original position or a whisker tighter, that way you
would keep it close to the original gear lash setting.

[DGXSER]

On the Type I 750 FD, they did use a spacer washer to set up the lash. But even then, it should only effect it if the torque is set by a distance. Think of what your trying to set and where the washer is going.

Anyway, on the Type II 750 FD (all 850 are type II) which have that phillips head screw mentioned, they used a crush sleeve inside to set the spacing by torque. So, if you do not mess with that screw and pull it apart, no muss, no fuss. That nut never comes into play with the driveshaft, so the spacing is not critical.

JMO

[3Phase]

On the Type I 750 FD, they did use a spacer washer to set up the lash. But even then, it should only effect it if the torque is set by a distance. Think of what your trying to set and where the washer is going.

Torque by distance? What is that, a measure of how far either final drive type will throw its parts and the rider after removing and replacing the input shaft coupler nut without checking the input bearing preload while tightening the input shaft nut?

Anyway, on the Type II 750 FD (all 850 are type II) which have that phillips head screw mentioned, they used a crush sleeve inside to set the spacing by torque. So, if you do not mess with that screw and pull it apart, no muss, no fuss. That nut never comes into play with the driveshaft, so the spacing is not critical.

JMO

Okay, the final drives are still relatively inexpensive and easy to replace but if you don't set them correctly you will, assuming you live, be replacing the final drive when it fails.

Removing the input shaft nut to seal the holes in the 750FD input coupler and add a larger washer changes the input pinion bearing preload the instant the nut is removed. The torque will have to be set while the bearing preload is checked and set.

The input shaft nut spacing isn't critical and won't affect the drive shaft unless the nut comes loose because it wasn't torqued and locked in place. You will have to be very creative to seal the holes in the 750FD input coupler and add a larger washer without removing the input coupler nut.

The Phillips screw on the Type II allows the removal of the entire input shaft and pinion assembly to check pinion depth and lash. If the input shaft nut is not disturbed and the pinion assembly shims are not removed or changed then the bearing preload and pinion depth/lash are not changed. The Phillips screw has nothing to do with it.


The Type I input assembly bearing preload and pinion depth/lash is set:
[#pinion assembly/housing shims]+ [#input shaft shims]@[torque_value].

The Type II input assembly bearing preload and pinion depth/lash is set:
[#pinion assembly/housing shims]+[crush washer]@[torque_value].

With either type of FD assembly the input shaft nut has to be set to the correct torque while the input shaft bearing preload is checked.

[gareth]

Now I'm wishing I had just cut up an oil filter o-ring and just stuffed a couple of pieces of it into the holes with some RTV. This had been Plan A, before I got all confident. Plan B was to do the puddle of epoxy thing that another poster listed.
Plan C was follow the instructions, RTFM, etc.. Looks fine so far, not sure what the symptoms might be if it starts to fail..

I put 160 miles on the drive today, mostly high speed slab, Route 78.
Really like the mod so far. First gear takes a bit of getting used to. I need to gun it a bit more and be patient or it lugs for a bit and shudders. I was never in first for very long anyway; just to get it moving and then click into second .Two thru' four are cool, I love my new overdrive fifth..
I need to develop a couple of new habits when changing down for sharp corners, just need to click down one more sometimes to make sure I have all the control that I need when I throttle out. The new ratios just take a bit of getting used to. I do sense a bit more "road feel" with the taller gearing, which is probably just a matter of getting used to "what/when/how much?" is happening at the rear wheel. Essentially just paying attention as if I am riding a new bike... Also, dropping a gear is necessary for that jolt of power that was always available with the old "top" gear at higher cruising speeds.
A few days and I should be fine with all the quirks..

Good Mod.

Like it.

Gareth.

[DGXSER]

Honestly Scott, Here is what I was thinking, I have a ring gear sitting in space, and a pinion gear on a shaft, that gets pulled into a sleeve to set the interface spacing. How far the top of the pinion gear is from centerline of the ring gear. That distance from the top of the gear to the plate where the FD meets the Swing Arm is the critical dimension to keep constant, all else being static. Now, removing the nut from above that plate, and the washer to it does not in itself change the critical distance. How much torque you apply to that nut could change it by how much it stretches the threaded shaft or crushes the nut. Thus the crazy term Torque by distance. Sory for the misguided terminology. But truly it is how it will work. So, removing that nut and the washer under it can not really change the interface point.

I know on the Type II that there is a crush washer as opposed to a spacer inside the sleeve where the pinion gear comes out that sets the distance by the torque applied. And yes I know little daddy yami worker measured that interface and crushed that sleeve until it was JUST so.

Now, the Official shaft drive manual says to apply about 72-108 ft-lbs of torque to that nut. I know if I applied the torque required, I could not have moved that FD around the wheel to save my life. The turning torque was SOOO high. So I replaced the washer with the stock one that was on it. Same effect. So I went...."HELP ME XS11!!" and many very smart folks on here told me to just tighten the nut until the FD got harder to turn, then back it off until it wasn't. So I did, just as I had advised Gareth to do.

This Thread Here

4k miles or so later (not alot to some folks I know) it was running great with no problems when the bike committed suicide/ attempted homicide on me. Put another one on another members bike using the same method, no problems.

[3Phase]

... 4k miles or so later (not alot to some folks I know) it was running great with no problems when the bike committed suicide/ attempted homicide on me. Put another one on another members bike using the same method, no problems.

I'm not trying to bust your chops. It's difficult to write a technical post without using a sfsf.

Final drives are touchy; used final drives are even touchier. They're not difficult to set up but they do have to be done correctly. Don't let them scare you! The final drives are easy to set up but they will fail if they're not done correctly.

As the thread you linked and I already explained several times before and in the post above: the coupler nut on a used final drive is torqued when the bearing preload reaches a few inch pounds (checked with a calibrated wrist or a beam-style inch-pound wrench), no more, and not by the lb-ft spec range in the manual for use with a new crush washer.

The nut will be a little loose on the input shaft and it will back off and sling around inside the coupler. Without the nut the input shaft, pinion bearings, lash and pinion depth will immediately assume dynamic instead of static positions and... well, you get the idea. Use Locktite or stake the nut on the shaft after setting the bearing preload.

When I did the 750 mod on my bike I took pictures. The mark on the outside of the original 1100 final drive coupler shows where it flexed and rubbed against the housing and destroyed the drive shaft.

Better XS11 u-joint for 750 final drive


That is the stock 1100 drive coupler in that picture so I don't really care how many people have done the 750/850 mod and not had any problems, the potential for serious trouble is there.

The bottom line is the 750/850 final drives are tough but not as tough as the original 1100 drive. The original final drive in mine was close to being hammered but a 750/850 drive would have already failed catastrophically. Enjoy the mod but don't get overconfident because it is not as strong as the original 1100 drive train.

[gareth]

Ah, Crap.
Now I gotta go back in there just to have a few fast miles worrying about stuff that other people might do. Instead of something I just did...