New question - how much does a final drive unit weigh?

[Mongrel]

I just want to confirm something. Assuming that you have an '86 or newer bike as I do (i.e. the output drive shaft is 20 splines) how swappable are final drive units (not the drive shaft) between different models of K75s and K100s? For instance, I could get a K100 final drive unit and put it on my K75?

I believe they're fully interchangeable, but couldn't find that for sure and just wanted to confirm that. Or would that not work? Sometimes I see part listings that mention the pinion gear ratio and I'm just wondering if that's being done for completeness' sake or if there are actually variable ratios.

[pdg]

There are a few different final drive ratios, usually the FD has it stamped on or near the flange to the arm. Which one you end up with makes a little bit of difference to the acceleration/top speed ratio.

I have a K100 FD on my 75 at the moment... According to the PO, that was a cheaper option than getting the bearings replaced in the original unit.

[frodef]

I have a K75C with drum brake. Is there a K100 model out there with a drum-brake FD that will give me a lower gear ratio/higher top speed?

[K75RT Keith]

Other than the number of splines changing, ALL the K series disc brake Monolever FDs are interchangeable.  ONLY differences are gear ratio and finish.  I don't remember a K100 with a drum brake in the U.S.  So, short of converting to a rear disc system, you may have limited options.
 

[Mongrel]

One more question. Does anyone know how much a final drive unit weighs (closed, dry) approximately?

I'm guessing maybe 20 lbs? Can't be much more because it clearly weighs less than the transmission and I know that weighs 35 lbs or so.