As a matter of interest does a K1100 alternator fit a K100? Is there any difference between the two?

yes i believe so ...but be verry carefull there are different depths - projections of the bell coupling .

there has been couple of documentations of that issue .

http://k100rt.aforumfree.com/t2260-pissed-at-myself-alternator-swap-results-in-bike-breakdown

STEVE1959 wrote:As a matter of interest does a K1100 alternator fit a K100? Is there any difference between the two?

The main benefit is the additional output of the K11's alternator over the standard K100's. Swapping the original K100 adaptor housing that houses the rubber monkey nuts to the K11 alternator will suffice, as the "driving dog" is the same part number. In addition, you must change the main 12 volt connection from a spade connector to a ring terminal. I've just located one at the workshop and will be fitting it upon my return. The difference is 33 amps compared to at least 50 amps. That's more for lights, action, camera, as well as heated grips...

So the actual physical size of the alternator is the same and it takes up the same amount of space?

It is a bit bigger in diameter and length but does fit.

Thanks to everyone for the information....