It would be interesting to compare the specs of the brakes on the K75 front end to those on an R65 front end.
Things we need to compare.
1. Piston sizes of both the master cylinder and the calipers of both bikes.
2. Disc size, and therefore where the caliper is mounted on the fork.
It might be that the K75 has a performance advantage due to the brake spec. Or it might be that the forks themselves have a better action.
I myself have contemplated putting a set of R65 forks on my R100, it would shorten the bike and make it a quicker 'steerer'
I actually have the yokes already - and the axle - and the deep dish carriers - but I have yet to tackle the headlight mounting issue with the R100. One change always leads onto another!