The 750 final drive mod

[jmnjrpa]

I had an idea on that one as I contemplated changing it out the last few days. I noticed that all conversion may possibly be done at the final drive. without messing with the drive shaft. Gonna tear a 1100 final drive down and compare it with the 750/850 I have tore down. I'm thinking there may be a "swap parts" only possibility to the final drive conversion. Will keep everyone informed and if it works will post pics.

[xschop]

The final drive input splines are shorter on the XS-750 FD to make room for the XS750 oil-ring interface....the reason for the spacer between the xs11 shaft and u-joint when sticking the xs750 FD on the XS11 swingarm....

IIRC, to put the XS11 FD on the xs750/850, you just need to remove the oil-ring on the 750/850 shaft and stick on the xs11 FD and be quicker off the line. Someone dragging an xs850 did this a few moons ago.

[fartypants]

final drive

Are the entire units swappable? Is their a difference in gear ratio ?

[xschop]

When you guys stick on the XS11 FD on an 750/850.... write it up
There is also a difference between the middle drives on the xs750/850 models D & E that the Yammie engineers changed the ratio to get the xs750/850 quicker off the line.....I know for a fact that it would fit the XS11 case...

[xschop]

Fyi

Hey J, the pinion drive spline counts between the 750/850 and XS11 are different inside the FD's and cannot be interchanged.

[jmnjrpa]

Xschop,

Ain't no bad against your mod. Being a machinist gives me an eye for possibilities. What I see is a possible swap of the input splines. Not sure yet how the input spline is coupled to the pinion gear. May not but I will check it out this weekend. If it were to work it would only add to your most excellent idea.

Thanks for the confirmation on the 1100 final drive to the 850 bike. I had not had the time to research it so that helps a lot.

[xschop]

The XS11 FD is an easier swap to the XS750/850.

But what I'm referring to is the drive pinion (part that goes between driveshaft and small pinion inside FD) has a different spline pattern between the 750/850 and 1100. I tried that route before simply adding the spacer between the U-joint and XS11 drive shaft (which is beefier than the 750/850 shaft)

[jmnjrpa]

Not sure

if I understood you. Did you say there is a difference between some 750/850 drives and others? That would be even better for some. Myself included as the change from 3.3 to 2.9 is a BIG jump. Thanks again.

[xschop]

No. XS750/850 FD = 2.9 ratio
XS110 = 3.3 ratio

Tear the 750 FD open and you'll see the problem, although the 750/850 and 1100 driveshaft splines match, the pinion drive splines are different between the two.... A 50 ton press may make them interface....

[jmnjrpa]

In this experiment the 1100 drive line and internal spline (on the outside of the final drive) would remain on the bike (the internal spline mounted to the 750 final drive pinion shaft - if possible).

[3Phase]

In this experiment the 1100 drive line and internal spline (on the outside of the final drive) would remain on the bike (the internal spline mounted to the 750 final drive pinion shaft - if possible).

I didn't photograph the two different input gear assemblies (I should have) but I did post some pictures of both external couplers here in this thread: Better XS11 u-joint for 750 final drive

Just a thought but are you thinking of using the 1100 input gear assembly with the 750 ring gear?

The number of teeth on the input gears are different so I was looking at something like that to get a 3.10 (I think) final drive ratio with the 750 ring gear and the 1100 input gear but I forget the details now. Maybe it was the other way around. The problem was that even if they could be interchanged the number of teeth would be wrong. The tooth count mismatch would make the original hunting pattern into a non-hunting pattern and the used gear faces would wear out pretty quickly even if they were set up correctly. It's not a big deal with all the cheap final drives available to play around with but I didn't pursue it any further.