Failed XS750 Final Drive (Images and video link)

[3Phase]

I have one waiting. I want to put some more miles on with the stock one first though.

So ... do you have a camera and a torque wrench?

You don't have to readjust anything at all in the final drive if you just take it apart and look at it.

The side cover nuts get 16 ft-lbs of torque and there are no gaskets, just a couple of seals and a large o-ring on the side cover. Remove the side cover and ring gear, take a look inside, clean and re-oil the parts and then use a wood or rawhide mallet to tap the side cover back into the housing and put it back together. Go slowly and tap evenly around the outer edge of the cover so the inner and outer seals don't get pinched or cut.

If for some reason you remove the pinion assembly the whole thing will come out as once piece but if you don't take it apart any further you don't have to check or reset anything.

You do have to put a very light film of Yamabond on the final drive case, the pinion housing, and on however many pinion shims are present so that gear oil doesn't seep out around the joint between the final drive housing and the pinion assembly. It won't hurt anything if you don't use the Yamabond but the final drive might develop a runny nose.

The shims between the pinion housing and the final drive housing are what's used to set the pinion depth, not the pinion nut and bearing preload. If you don't change, add, or remove any of the shims then you don't need to worry about resetting the pinion.

[natemoen]

Don't know if I want to get involved in this pissing contest.

[3Phase]

Don't know if I want to get involved in this pissing contest.

Nate, it's not a contest of any kind and it's a lot safer and easier than triple-cleaning the carburetors. There are no adjustments besides the torque on the side cover nuts and the final drive will not leak highly flammable liquids or vapors.


Here's an overview graphic from the shaft drive manual. I cleaned it up a little from the PDF. It can be saved and magnified it if you have trouble reading it:-

Yamaha XS750 shaft drive manual appendices.

Middle and final drive tightening torque, gear lash and bearing preload chart for Type I and Type II units.

[TopCatGr58]

You can keep your fly closed!

Hey Nate,

Scott is just suggesting that it might be prudent for you to take it apart just to be able to inspect the innards for any signs of pending failure or excessive wear prior to putting it into use, that's all! I think it was you that had stated that you weren't sure what condition your 750FD was in? I would think that anybody doing this swap would want to be sure that they were putting in a good condition FD and not one that had possibly been thrashed by a PO on a 750/850! I think for them to be shipped thru mail or ups, that they have to be drained first, so you can't see the condition of the OLD oil when you get it.

T.C.

[3Phase]

Trying an XS850 Final Drive

I won an XS850 final drive on eBay yesterday for $9.99 + $19.36 S&H and it's already on its way to my door from Las Vegas for a grand total of $29.35 split, stacked, and delivered.

The XS850 drive looked okay in the pictures but the teardown and inspection will let me know if it's good enough to use for anything except a doorstop or a paperweight. In the meantime it's time to do some more riding this weekend and enjoy the power and acceleration of the XJ final drive!


http://cgi.ebay.com/ebaymotors/ws/eB...m=110735207711

[GARTHXS]

Don't do it your bike will splode!!!!!!

[3Phase]

Don't do it your bike will splode!!!!!!

You know, Garth, all things considered that's prolly the best thing that could happen to it... so it won't.

Paraphrasing Murphy's Ultimate Law that I read somewhere on the 'net but can't remember this time of night: If something can go wrong but doesn't it's because you would have been much better off if it had failed.

[3Phase]

Toaster Parts

UPS made a delivery this afternoon!

There is no known mileage but the 'new' XS850 final drive looks clean from the outside and the gear lash and bearing preload are within specification.




Here's the first look inside the 'new' XS850 final drive and it looks burnt.

There are no metal bits anywhere and the gears and bearings look good so I might get lucky and it will clean up and be okay.

[crazy steve]

Kinda looks like the lube changes may have been rather far apart... Not that that means it's bad...

Nice smiley....

[3Phase]

Nice smiley....

It does kind of bring out the sludge doesn't it....

The donor bike was out in Las Vegas so it was probably run hot more than a few times. The residual oil looks and tastes like a good grade of gear oil with a bouquet that has a slight eau de carbon to my nose with delicate hints of an original factory fill or something of a very similar vintage.

[cywelchjr]

It does kind of bring out the sludge doesn't it....

The donor bike was out in Las Vegas so it was probably run hot more than a few times. The residual oil looks and tastes like a good grade of gear oil with a bouquet that has a slight eau de carbon to my nose with delicate hints of an original factory fill or something of a very similar vintage.

Eewww, that makes me want to go out and change all my fluids just because. That's the kind of stuff that's scary about ebay, or any non-local buying for that matter (or even the local junkyard), you don't know what the last guy did to it. Even if it looks clean when you get it, how do you know the PO didn't flush it out good and run some nice clean gear lube through it and then drain it before sending it off to you? Of course I guess as long as there are no signs of heat damage to the gears and bearings or seals then it may well still be just fine anyways.

[latexeses]

eau de carbon

Early Cretaceous vintage perhaps?
No hint of comet dust I assume?

[3Phase]

Early Cretaceous vintage perhaps?
No hint of comet dust I assume?

There might have been little bits of dust but the P.O. mostly got iridium.

[latexeses]

the P.O. mostly got iridium

Man, I was really hoping you would do that! Well done!

[3Phase]

Man, I was really hoping you would do that! Well done!

They just write themselves! And don't forget to tip your waitress!



Cy, this is why I've taken apart both of the final drives I've bought before I even wasted my time trying to clean them up and put them on the bike.

If you going to check the drive just remove the ten nuts and washers on the side cover. There are two cutouts in the side cover for a couple of flat-tip screwdrivers so you can lift the cover right out of the housing along with the ring gear and the side bearing. With the cover off you will be able to see everything for yourself and decide whether or not it's worth lacing it back up.

Be gentle because the bearings are steel fitted in a precision-milled aluminum housing. If the drive doesn't easily slip apart and lightly tap back together with a rubber mallet or a block of wood then find out what's holding up the process.

Do not use a steel hammer on the gears, bearings, the aluminum housing or the side cover.

The side cover is made so that it will only go on the housing in one position so you can't mess it up. Slowly tap the side cover down using a star pattern until the threads on at least three opposing studs come through far enough to start a nut on them.

Finish seating the side cover by tightening the nuts in a star pattern one turn at a time while turning the input coupler to make sure the gears and bearings don't bind.

When the side cover is fully seated, take the nuts off and put on all the washers, then put on all the nuts and snug them down finger tight.

Using a star pattern, torque the nuts in two or three passes while checking the input coupler to make sure the gears/bearings don't bind.

That's it, you're done. Put the final drive back on the bike, grease the splines, fill the drive with oil and go ride.