1100RT or RS final drive for 1100GS

[Fritz58]

Just bought a final drive for my project, described as being for a GS however the ratio is wrong (31/11) and it has the disc/ABS ring attached. There isn’t one currently so I thought it looked OK. The drive shaft doesn’t seem to locate and the pivots are a loose fit as well. I assume I’ve been sold the wrong part and year. Anyone know if this is at all useable, it doesn’t seem as simple as just removing the disc/carrier and even then the ratio is wrong. Thoughts and input appreciated.

 

[ThreeDawg]

Well if it is for a GS it should have lugs to mount the possum scraper. Sounds like you might have an RT one as you say with the disc fixed to the wheel, but I would be interested to find out the exact bike. I have one off an 850RT on my 97 GS and it fitted straight on (albeit changing the gearing), but I do recall that the shaft stub came with different numbers of splines depending on the year.

I didn't know there was a 31/11 ratio available. Might be a tad high at 2.81:1. When I was trying to figure out what I'd been sold I rounded this up:

R1100GS standard gearing 33/11 (3.0:1)

Current FD (R850RT?) 32/10 (3.2:1) 6% lower.

R1100RT, R1150RT 32/11 (2.91:1)

R1100S 33/12 (2.75:1)

R850R 37/11 (3.36:1)

I think these are correct, if anyone knows different or can add to the list I'd be interested.

 

[Ian J Hartley]

The research was done a long time ago by Anton Largiader.

https://largiader.com/articles/gearing/

 

[ThreeDawg]

Interesting. Anton has the 32/10 to be off a K75, but mine is clearly off an oilhead as the earlier FD has a completely different housing. An omission, not an error. There seem to ve two listings for the 11xxRT - different markets? Police versions?