Final drive Solution

[xschop]

Well, here it is folks. A bolt on solution to change your final drive gear ratio. you could use early seca, xj maxim, or virago drives, but you would have to reweld shock mounts (not fun). I stumbled on this one,thought it was an xs11 (just by looks) then noticed the pinion drive (is different from the xs11's) so rotated it and sure enough 2.9:1 and matches the xs11's dimensions including shock mount points.

[xschop]

pinion drive

I removed part number 12 from the schematic and filled in the "port holes" with epoxy and applied gasket sealer to the splines. You have to do this procedure or the 80-90wt gear oil will leak out because the xs750 shaft has a rubber stopper on it for this. However, you can't use the 750 shaft because the u-joint splines don't match the xs11's u-joint. So I experimented with the xs11 shaft and it is 5/8 inch too short, because of the recessed pinion splines on the 750 FD. I am having a custom one made as we speak. But in the mean time, I put a 5/8 inch collar on the 21 splined u-joint end which gives plenty of grab at the u-joint union and safely seats into the 750's pinion drive....I have really driven this thing hard in the past couple of days after taking it easy the first few....I am not changing this setup...It is very smooth and driveable with less rpms on the xs11 motor, not to mention my gas tank is happy....

[MAXIMAN]

That ROX! Off an XS750 huh?

[xschop]

It now makes sense

If you turn the 750 hub over is where you tell the difference between the two. the 750 has a smaller diameter gear than the xs11. I wondered all week long why Yamaha changed from the gas sipper to the gas hog, They wanted to own the 1/4 mile back then. So the xs11 hub is a redesigned xs750 hub with a higher gear ratio....chop

[GNEPIG]

.. hey Chop, cool research, i'm diggin the outcome and cant wait to try this. i was wondering if you have come across any of these F Ds that geared the bikes lower? i'm lookin forward to some better 1/4 mile times with one of my bikes, as i have found that i get a better time by not shifting into 5th.
..also, any cool ideas on how to lengthen the whole swing arm assembly, as this would help dampen shaft jacking and help prevent wheelies on take off.

[xschop]

virago 1100

to lengthen,this would be the setup. There is a final drive from an seca 650 turbo that was like 4:1 ratio which could be adapted to the xs driveshaft....man, that would launch so sickly....

[GNEPIG]

.. yeah, launching sickly, something like that, i will look into it
thanx

....man, that would launch so sickly....

[pggg]

Yeah Chop I've heard people on this website claiming that 750 final drives weren't compatible with 1100's - yeah right. Is your current gearing from an E or D? GNE, maybe the 750 - 850 - 1100 gearboxes have interchangeable cogs, change ratios that way, sh**t that would be tricky

[xschop]

interchanging

I can see why people said it din't fit. The pinion drive splines are different. Problem is now solved. BTW, I rode to work this morning and intentionally got into 5th gear, doing 70, right before the 1/8 mile uphill run before my exit then gunned it to see how it would act. It pulled me up hill accelerating hard hitting past 100 and wanting more before I had to get of the the throttle and exit. Another thing I like about the change is during take off at traffic lights while turning left or right.It is very smooth in 1st gear and doesn't wind so high and become jerky if you're turning sharp and your wrist is stretched in an akward position...

[50gary]

XSchop, great bit of research/work, I'll be looking for an XS750 rear drive unit.
Cheers, 50gary

[xschop]

FD

just make sure you rotate the pinion drive ensuring you have the 2.9:1......before you open your wallet

[TopCatGr58]

Hey Chop,

Great work/research!!!! I have a question, and remember, I'm no engineer! You say you have to lengthen the XS11 shaft by 5/8" so that the FD splines will reach the 750's recessed drive.

My question is...... is the flex location of the Ujoint that critical where it's located, or would moving it rearward 5/8" cause any contact problems with the driveshaft housing?

I would think it would be easier to use a 5/8" spacer where the Ujoing bolts onto the Middle Drive flange, using longer bolts, but again I don't know how critical the location of the Ujoint angle or the possible contact with the shaft housing swingarm is??
T.C.

[79XS11F]

So this mod dose what?
Gives you more speed at lower RPMs or quicker acceleration or both?
Is the 750 Shaft and parts heavy enough to use in the 1100 over the long haul?
Rob

[Trikerneil]

TopCatGr58

FWIW I would think the position of the UJ is critical as it's centreline is on the centreline of the swingarm pivot. Moving it back 5/8" would mean the driveshaft would want to lengthen/shorten as the suspension moved. You'd really want a moveable spline somewhere.
You could possibly fit a 5/16" spacer at the middle gearbox and pull the spline out 5/16" where the UJ is attached to the driveshaft. That would give you abit of movement.
I don't know about clearance issues as I don't have a swingarm on the Trike.

[xschop]

Hi T.C.

The spacer was my first thought, BUT IT WILL NOT WORK!, There is @ 5/16 distance between xs11 u-joint and it's own shaft housing. I think the other guy here is also thinking correctly @ shaft travel if you move the u-joint with a spacer if you could. BUT, you can cut the u-joint splines and reweld 5/8" spacer between that, however you would need a jig of some sort to ensure a perfect center reweld. I am having another xs11 shaft cut and reattached to a 5/8" LINE-BORED sleeve and ends rewlded. I told the machinist to make the sleeve diameter no larger than 1/4" of the shaft diameter(that will leave 1/8" on each side to clear the xs11 inner shaft housing) I will be the Ginea Pig on this one too The real easy solution is to find a shaft that is exactly 10 1/2 to 11 inches long....this would be plug'n'play.... I am going to the yamaha shop today, my friend said he has a big box of them for me to check.....chop