FD swap copper spacer

[BA80]

I've seen several people questioning the longevity of the DL spacer made from copper pipe when doing the 750/850 FD swap. I changed out my swingarm today because I suspect it was bent and got a good look at my copper spacer that's been in there for about 5 years and 50,000 miles or so.

It looks exactly like it did the day I put in in there.

This should put to rest the worries some of you have.

[DiverRay]

Greg, I think I see about 0.002" wear on the end! You may need to replace it in about 5,000,000 more miles.....

[BA80]

Greg, I think I see about 0.002" wear on the end! You may need to replace it in about 5,000,000 more miles.....

Ha ha.......that's just the mark from the tubing cutter I used when I made it.

[3Phase]

It looks good, Greg!

The shaft is made of some seriously hard metal and the spacer is not a stressed part of the driveline so it wouldn't have much wear if you put another 200,000 miles in it. The wear would be on the comparatively softer yoke splines and the bevel and the raised lip on the spacer at the shaft/yoke face shows if the shaft's been wobbling in the yoke. To know if it's worn or tapered you'd have to know its original Length and the ID/OD, then compare the current dimensions.


Personally, I never worried about the spacer, it's the yoke and driveshaft splines I was worried about and measured when I did the first '750 conversion. Here's an old thread from 2008, the 2nd post is from XSChop but he had a chain-drive XS11 so he probably doesn't know anything about shaft drives or the '750 mod:-

Better XS11 u-joint for 750 final drive


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[BA80]

I seriously doubt 2.25mm less engaged spline is going to be an issue.

[3Phase]

I seriously doubt 2.25mm less engaged spline is going to be an issue.

You need to check your calipers, the spacer is a lot longer than 1/10" and so is the loss of spline contact.

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[BA80]

There is no need to jump through all these hoops when a simple spacer (copper bushing) can be made to effectively accomplish the same task. Upon studying the Eleven’s splines that interface with the U-joint yoke I could see that about 24 mm of spline is being utilized. Notice the 3mm or so splines beyond the circlip groove are not used in the OEM configuration. These splines protrude past the u-joint yoke receiver and a circlip holds them in place. I have yet to ascertain why the circlip is there. There is no way for the shaft to ever come out of the yoke once in place. The circlip is appears to be some “over-engineered” design.



Next I cut a ¾ inch copper sweat coupling (like you’d find at a hardware store)…I cut it 16mm long.



Then I slipped it over the shaft. At the drive end of the U-joint spline I slipped a 5/8 x 3/4x 1/16 O-ring to act as a retainer for the copper spacer. It will hole the spacer in place as the shaft spins reducing wear to the copper. I also coating the shaft splines in that area the collar covers with RTV to help hold the copper in place and reduce vibration. I don’t know that this is nessecary but It can not hurt. Then at the yoke end of the collar I slipped another O-ring. In theory this will keep the copper from rubbing directly against the yoke housing and should reduce wear to the end of the collar. And again – if the O-ring fails overtime it’s no big loss. The o-ring can’t hurt anything…it can only help.





After all this modification you can now see there is still 21.5 mm of spline length to engage the yoke. We’ve only lost less than 3mm of spline length. This should barely compromise the strength of the spline interface. Plus using this mod method we have not compromised the torsional strength of the shaft.

[BA80]

It's actually 2.75mm. I was working from memory. I'll give you .5mm.

[dbeardslee]

Thanks for posting this! That's the same kind of spacer I've got on mine, and my peace of mind index just shot through the roof. That tall gear in the rear will spoil you real quick - I wouldn't want to have to go back to the stocker.

[BA80]

I knew some were worried about it and no one else had posted any new news about it. There is absolutely no wear on it. That lip you see on the top is just as I said, from the tubing cutter I used when I made it. The shap edges from that cut are even still there.

BTW, I've been meaning to ask someone with a Standard with the 17" wheel how it works on there. The Standard with the 17 and stock FD are virtually the same gearing as a Special with the 16" and the FD mod. So, the Standard with the mod has to be even HIGHER geared.

[dbeardslee]

I knew some were worried about it and no one else had posted any new news about it. There is absolutely no wear on it. That lip you see on the top is just as I said, from the tubing cutter I used when I made it. The shap edges from that cut are even still there.

BTW, I've been meaning to ask someone with a Standard with the 17" wheel how it works on there. The Standard with the 17 and stock FD are virtually the same gearing as a Special with the 16" and the FD mod. So, the Standard with the mod has to be even HIGHER geared.

I've had Betsy up to 135 with the FD mod, and she still had some left. I ran out of guts - she didn't. I'm positive that the top end is somewhere over 140. But where I really like it is on the lower end. First gear is actually usable for something besides going the first fifty yards, and she's doing around 4k rpms at 70 mph IIRC, so highway cruising is sweet. If I flog her I get just shy of 30 mpg, but if I maintain a steady speed she's been as high as 45 mpg. It's a very sweet mod.

[3Phase]

I haven't figured out what the driveshaft clip is supposed to do, either except as a safety and assembly/disassembly aid. It keeps the driveshaft from sliding out of the swingarm tube and stabbing you in the eye when you look up into the swingarm to check the splines after removing the Final Drive, so you don't have to try to thread the shaft back into the yoke with only one remaining eye.

In your spacer and driveshaft spline measurements you forgot to subtract the 7mm entry bevel in the u-joint yoke splines.

24.3mm - 7mm = 17.3mm of 'active' spline length.







The driveshaft spacer for the '750 mod has the same effect on the driveshaft as the hub seal on the Final Drive output. When Tod stripped the hub at 11,000 feet no one was commenting about how pristine the seal looked and how little wear was evident.

I guess a better example would be the assorted shims, collars and spacers in the Middle and Final Drives that don't actually have drive surfaces to turn the rear wheel but the hub seal works for a recent rolling example of where not to look for wear in the drivetrain.

Doug,

The top end with the '850 drive is above 140.

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[motoman]

Good info there Greg..........well least for those who do the mod. kidding as you know, but here 30-45min. from some serious mountain twisties the stock final and third-fourth gear keep these ole' scoots happy.......and WAY quicker on the straight-line accel.

[BA80]

I didn't forget to ride 50K miles with both eyes and do a tear down for real world proof.

If you look at Maximans pics with BOTH eyes you will see that the measurement was taken at the ridge of the splines which also doesn't take into account the additional contact in the valleys. Of course there's always that pesky groove that the useless snap ring fits into so I suppose they cancel each other out.

Looking for another .5mm?

[3Phase]

Looking for 0.5mm? Uh, no, a full 7mm, no zero-points.

You do get to use the virgin driveshaft splines with the yoke but you lose 7mm at the yoke entrance so it's still 7mm short of 24.3mm.

Where are Maximan's measurements for the spline lands, peaks and valleys? It's finally cooling off here and it's still over 107F so I probably missed them but if he has real-world 50,000 mile measurements of driveshaft and yoke spline wear after the '750 mod that's fantastic!

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