hi all will a k1100 COMFORT SEAT fit my k100 rt 1986 without any modifacation if not can anybody tell me anywhere in the uk i might find a comfort seat that would fit many thanks from paul.

The only modification needed will be to trim the bottom of the seat or cut 1" of the tool tray under the seat.
This is minor modification and I choose the option to trim the seat on my 1986 K75.
You will have to get the proper hinges for the seat too. The original K100 don't work with the comfort seat. The bike frame is OK, you just have to replace the back hinge.

Have a look for the 100 LT Comfort seat. That should fit without any modification. It worked for me and my 100 RS...

My seat is a BMW comfort of a K1100lt and not a K100lt.
This seat will work on a K100 too with the small modification on the pan.
The cut of the 1" bulge doesn't affect the comfort. If you want to keep the seat original, you can instead cut 1" of the height of your tool tray.
You can find used tool trays on Ebay if you don't want to modify yours.
I just found that the K1100 doesn't have a tool tray and this is why the seat has the bulge.
Now you know that you have 2 options. K1100lt or K100lt

Here is some picture taken when I was fitting the K1100lt comfort seat.

thanks for all the info will try and get the Comfort seat and have a go at fitting. again many thanks.
paul

Hmm
good info that, I find the RS seat a bit on the tough side
on long rides