Hi all, I have recently acquired a very tidy '87 K100RS. The previous owner bought it in Scotland and travelled extensively throughout the UK and Europe before shipping her home to New Zealand twenty years ago. He owned it for 24 years with two subsequent owners before him. It will stay in my possession for many years alongside stablemate, my 2002 K1200RS which I've owned from new.
It has Ohlins rear and KSS Race Tech springs up front, and braided lines fitted. I helped last winter with the O-ring and main seal replacement although the main reason to go in was the starter sprag which needed attention. Splines were inspected and lubed at the same time. Clutch was inspected and at 52,000 miles was reinstalled untouched. Since landing in my garage I have replaced the fork seals, Hall sensor cover gasket, (Still leaking in the area but not this gasket  so must be the timing case/cam chain cover) full brake flush and all oils. 
The only other issue to show up is a sticking front brake MC piston. It does retract so the pads do not bind on the rotors but the brake light stays on which was the giveaway that something was amiss. I have tried a little lube from the lever end but to no avail, so looks like the MC is coming off for a proper dismantle and clean. Can someone point me to a thread that can help me on my way please. 
I have been lurking about here for a couple of months and look forward to being involved with the forum.

Greetings KiwiK100 good to have you aboard.

welcome aboard

sounds like a nice bike

the reservoir for the master cylinder is where you might inspect the 2 holes that lead to the master piston ...if one of them is blocked ..ie the one at the handle end ,,,it might restrict the piston from returning fully ....(equalizer tube ) also be aware not to over fill the reservoir

there are threads about this all throughout the forum

try the "search" feature

and good luck

Thanks for the welcome and the advice. In hindsight I should have left my question to a new thread. Anyway, removed and thoroughly cleaned the MC today and put it all back together solving the problem. Interestingly the rubber diaphragm seemed to have swollen and did not want to fit back onto the reservoir cap, but a thorough clean and left to fresh air for a few hours and it shrunk back enough to fit. 
BTW I looked for the search button and can't find it. Obviously I can't see the forest for the trees so if someone can point me in the right direction...

Welcome to the forum too. Its good to have a lurker coming in from the Kold. Don't be afraid to ask questions, everyone is very helpful and friendly.

You need to go to the forum page to find the search function.

I think rick means the "portal page "  found here

https://www.k100-forum.com/portal




edit

both the portal page and the main forum page have the search box