Variation of the 750/850 final drive mod

[TopCatGr58]

Okay Scott,

I've never seen that extension for the U-joint...just the COLLAR that is in the MOD text! Where did you get the donor section?? How did you do it? I know you welded it, but did you stick the male end of the drive shaft into it to help align the parts so that they would be straight while welding, and I would assume some well placed TACK welds first before laying on the heavy beads. If this technique replaces the COLLAR, then looks like we need to add this to the tech tip as an alternative mod!

T.C.

[3Phase]

T.C.,

When I first did the '750 mod I bought all the recommended parts but I didn't trust the spacer idea so I cut the barrel off the yoke from a bad u-joint and extended the splines the full length of the driveshaft again.

At the time I wanted it to be stronger than just the spacer but I also wanted to be able to undo the mod. I used the driveshaft to hold the parts together and aligned while I drilled and pinned both pieces with a couple of broken 1/8" drill bits, then covered them with JB Weld. The JB Weld crackled off like I thought it would but you can still see one of the holes in the yoke and it still has the pin in it.

When I decided it was time to make it permanent I brought the driveshaft along to the welder's shop so the parts would stay lined up through the heating and cooling.

However it turns out it uses up two XS11 yokes so don't mess up.

Cut The Yoke


Dress And True The Spacer


Check The Splines


Extended Yoke vs Spacer


XS1100 U-Joint Yoke Extended



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[TopCatGr58]

Hey Scott,

Thanks, I've copied your post to the Final Drive Mod tech tip, and SOMEDAY I'll fix the photos in the Forums version of the tip!

Thanks for providing the "HOW TO" and photos.

After seeing it, I "was" thinking that perhaps one might NOT need to sacrifice another U-joint Yoke?? I realize NOW from viewing your photos that when the OEM shaft and yoke are assembled, that it sticks out THRU the inner edge/end of the yoke towards the U-joint...that way the Keeper Expansion ring can open to help secure the shaft in place. I was thinking that perhaps one could cut off a lot of the the OEM yoke piece, then put a simple plain PIPE/Tube section in between the cutoff part of the yoke and the NOW splined end piece, both getting welded onto the OEM yoke. The expansion spacer would have a wide enough ID to NOT engage the splines of the driveshaft, and would still put a major amount of the YOKE spline section very close to the full engagement point on the driveshaft splines. And with the wider Expansion section/area in between, the expansion RING can still have room to expand to help secure the driveshaft in place.

Anythoughts on this approach??

T.C.

[3Phase]

Kurt,

Nice looking mufflers! No Harley people are crying, they got yanked and trashed! Are they regular mufflers or is there a catalytic converter? You can cut out the cat but it's not simple.


T.C.,

I have better pictures if you need 'em, I was pretty brutal with the compression and I think I scared poor Kurt, he's cutting up mufflers to make muffler bearings!

You can put on the snap-ring if you want to, I just leave it off. The snap-ring makes it a pain in the keister to R&R the driveshaft to grease the u-joint yoke splines while I'm changing the rear tire and greasing the coupler splines.

I'm not dumb enough any more to let the driveshaft fall out of the swingarm or freak out trying to figure out how to re-index it and put it back in. When I pull the Final Drive I pull the driveshaft too so I can clean and paint all of the splines with fresh Moly-60 paste. I fill the 'groove' cavity in the u-joint yoke with regular moly grease and repack the Final Drive Coupler before I put it back together with the new tire.

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[Rasputin]

Nice work Kurt! I think the discussion on the final drive mod should be moved to a new thread to avoid the hi-jacking of this one. I know I have a few things in mind that may be of interest of that subject, but this is your thread so I will leave it be.

[TopCatGr58]

Okay Ras,

NEW THREAD NOW! Scott, I know you're fingers are sore from exposure to your solvents and such, so you can respond later, but you didn't actually answer my question about whether the technique I suggested about cutting off more of the OEM Spine Yoke portion....putting the spacer on, then welding the spines back onto the end of the spacer would be an acceptable extra Yoke Sparing technique and still provide enough spline depth and yet proximal enough to the shoulder part of the driveshaft spline area to provide enough grip and stability of the spline end of the driveshaft to prevent wobbling/wearing out of the splines of the yoke/driveshaft that "MAY" occur with just the use of the original copper spacer collar technique that only engages the end 1/2 of the splines of the driveshaft?? Sorry for the run on sentence/question!

Ras....you had some ideas, let them fly!!!

T.C.

[3Phase]

There are no problems with your sentence structure, T.C., you're writing as any adult would write and speak unless they're semi-literate, intoxicated, or both but I can loan you a bag of carriage returns and line feeds until you get your keyboard fixed.


XS1100 u-joint assemblies are still plentiful, use the regular spacer that's recommended in the mod until you find one with a bad u-joint cross that you won't feel bad about when you cut it up.


If I understand your suggestion:
Cut the splined yoke barrel a little longer.
Weld a non-splined spacer to the yoke cross at the barrel cut.
Weld the yoke barrel to the spacer.

Yes, you could do that. It wouldn't be very strong and the driveshaft would only engage the splines in the barrel stub. I think just using the spacer to do the original mod would actually be better unless you're really good at welding to cast iron.

The splines in the yoke run full length from the yoke cross to the barrel's tail and they're the same length as the driveshaft splines but:

Some of the u-joint yokes are one piece of cast iron with the splines machined into them.
Some of the yokes have a cast iron yoke cross with a steel barrel welded to it, then the splines are machined through both pieces.

Where I cut the barrel was right at the weld for the two-piece yoke but it would be right where the casting flares into the yoke cross on a one-piece yoke.

If you cut the barrel any longer it would have a flare of cast iron at one end that you would have to grind down so you could weld it to the spacer or you'd be cutting through the weld that held the barrel to the yoke and you'd be welding the spacer to part of an existing steel-to-cast iron weld.

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[CaptonZap]

I'm, not them, but I can type, so here 'tis.
All of the following is based on my experience of past years, and in no way should be taken as soundly engineered advice.
The problem with the spacer is that the splines are not engaged full length, and depending on the clearance between them, they can develop a rocking action when influenced by an out of balance condition in the U-joint.
The length of the engaged portion of the splines, after the spacer is installed is, in my opinion, more than adequate to handle the torque developed by the engine, so that is not an issue. Unless one treats their bikes like 3Phase does.
The method of cutting off the spline collar and welding a sleeve between the two pieces would work, but it is two welds with attendant distortion problems to deal with. If you have the tubing and a lathe, a tube with a close sliding fit on the OD of the splines, welded to the end of the U-joint, would probably cure the rocking, depending on the closeness of the fit, and only be one weld, with any distortion being easily corrected with some judicious tapping with a brass hammer. As long as there was no lengthwise bending slop, and the splined shaft could be removed, you would have fixed the problem. If doesn't have to be perfect, it just has to have no lengthwise bending play.
In other words, the added tube doesn't need splines, it just needs to keep the U-joint from rocking on the shaft.
That's my take on it. YMMV
CZ

[BA80]

Been running the copper spacer for about 4 years and better than 50K miles. Don't think this mod is worth the trouble. Over kill.

Just my opinion though. FWIW

[trbig]

Been running the copper spacer for about 4 years and better than 50K miles. Don't think this mod is worth the trouble. Over kill.

Just my opinion though. FWIW

Been running mine over 6+ years of HARD service with over 150k miles. I've destroyed a 750 final drive and gone to an 850, but the yoke is fine and still am using original copper collar. Agree with Greg. (As much as I hate to say it) Looking to spend time and effort on a non-existent problem. But if this gives you peace of mind.. So be it.

[3Phase]

That's great! I'm glad y'all have gotten the mileage you have but you make it seem like it's some kind of onerous, time-wasting security blanket. Don't do this mod! Seriously! I really don't care how many bikes you've wrecked and parts you've broken, this mod obviously bothers you on some level so don't do this mod!

As far as the time involved, how long did it take to go to the store, pick up a spacer for the regular mod and then pull the pinion assembly to seal the oil holes and torque it back down?

I wasted about an hour going to the store but after I decided the spacer wasn't for me it took maybe ten minutes to cut the splined spacer off a bad u-joint, then drill it and pin it. It took less than three minutes to clip two aluminum spiral nails for oil hole plugs and mix the JB Weld.

That's roughly thirteen minutes from one to done with no disassembly, no reassembly, no re-torque. It took another ten or fifteen minutes to mount the drive and the rear wheel and I did have to wait overnight for the JB Weld to set but there's not a spec of yellow metal anywhere in my drivetrain and all of the splines have full-length engagement.

During one of the rear tire changes when I was doing the spines I noticed the five-year-old, seventy-thousand-mile pins were getting loose in the yoke so I took it down to have it welded. It took the welder less than five minutes to weld it but I had to wait overnight because he was busy and I just dropped it off then picked it up the next day. It cost ten bucks and I'll never have to mess with that particular part again.

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[Rasputin]

Myself, it was not so much that I had any better idea's just a few thoughts. I really like this idea but I want to be sure before trying it.
What RPM does the drive shaft actually see at 8500 in high gear? At what point should a welded joint have to be balanced? What kind of vibration would a very slightly out of balance weld cause? (we all know a simple engine mount or exhaust seal can cause so many issues). If the drive shaft was out of balance would it, in turn, hurt the final drive joints?
Is there a replacement u joint that may have a longer piece already installed on it? Those nissan/toyota or whatever u-joints may have this issue already solved.
Cast u-joints vs steel? Can we get steel ones or are we stuck with cast? Who do you know that can weld Cast? Not many that can do it successfully, I will guarantee!
I just thought maybe something we could mull over would be the best of all worlds when it comes to this great mod!

[BA80]

As far as the time involved, how long did it take to go to the store, pick up a spacer for the regular mod and then pull the pinion assembly to seal the oil holes and torque it back down?

Suit yourself. Whatever blows your hair back.


BTW.......... How's that engine coming?

[3Phase]

Suit yourself. Whatever blows your hair back.

I did, by cracky!

BTW.......... How's that engine coming?

So far the engine's doing great but I had to run around town today to get my heart meds and other stuff.

.

[3Phase]

Myself, it was not so much that I had any better idea's just a few thoughts. I really like this idea but I want to be sure before trying it.
What RPM does the drive shaft actually see at 8500 in high gear?

I don't know, my brain hurts. A WAG would be somewhere around the average electric motor RPM of 3,450 but we can play ratio math tomorrow if you want.

At what point should a welded joint have to be balanced?

When it's not true and square or if it's bent. You'll know the instant you try to put the driveshaft into the u-joint yoke because the driveshaft will NOT fit and seat if the two parts are welded even slightly out true and square or if something is bent.

Unless you see gross slobber or chewing gum welds there isn't enough mass in the weld or the u-joint yoke to worry about balancing a weld at driveshaft RPMs but you can take it to a driveline shop and have 'em spin it up and balance it.

What kind of vibration would a very slightly out of balance weld cause? (we all know a simple engine mount or exhaust seal can cause so many issues).

It would be a slight vibration that you couldn't feel until it had worn the u-joint cross, yoke, and the Final Drive coupler but by then it would be a big vibration.

If the drive shaft was out of balance would it, in turn, hurt the final drive joints?

It depends how far out of balance it was. Again, there isn't enough mass in the u-joint yoke to go out of balance even from a bad weld. If there's a problem it's more likely to be because the extension was welded to the yoke out of line or off-center but then the driveshaft won't seat in the u-joint yoke. You wouldn't be able to ride it.

Remember, the weld is next to the u-joint cross, not out in the middle of the driveshaft where it can really shave the pooch if it's off by a pico-pound.

Is there a replacement u joint that may have a longer piece already installed on it? Those nissan/toyota or whatever u-joints may have this issue already solved.

There is a new u-joint cross available so there may very well be an off-the-shelf splined yoke that would fit the XS1100 driveshaft.


Part Number: PUJ 392
Product Line: NAPA Ujoints


It looks like the NAPA u-joint has a Zirk fitting but that could just be a generic image.

Cast u-joints vs steel? Can we get steel ones or are we stuck with cast?

The u-joint yoke is cast iron, the splined barrel can be cast iron or steel.

Who do you know that can weld Cast? Not many that can do it successfully, I will guarantee!

Goosfraba....

Welders have to eat too. If you can't do it -- I cannot -- they're in the phone book and some of them advertise.

I just thought maybe something we could mull over would be the best of all worlds when it comes to this great mod!

They're all good thoughts, Ras!

To move from the mechanical engineering side, look at the length of the copper spacer in the '750/'850 mod and notice that only one-half to two-thirds of the driveshaft splines are engaged in the u-joint yoke.

Now imaging taking apart a TCI that's been absolutely troublefree for thirty years to reflow the original solder joints and replace the old components with new ones, but they can only handle one-half to two-thirds of the original designed maximum sustained electrical load. Of course it will work. You know it will work and so do I because the TCI is a solid design so it'll work and it'll probably keep right on working for a long time even at one-half to two-thirds of its original designed capacity.

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