My 1985 K100RT had been sitting for a couple of years and when I grasped the front brake lever, it wouldn't move. Used more pressure and suddenly the lever lost all resistance and just flopped back and forth with no caliper response. Removed the lever to find the piston solidly seated deep in its bore. There was also no fluid in the master cylinder. There seems to be no way to extract the piston, short of removing and disassembling the entire assembly. It is not  obvious how to remove it. Looks like the grip must be removed so the assembly can slide off the handlebar. Hope someone can clue me in.

Hi John ,Removal of master cylinder is what you need to do, you will find out on forum if you dont have a manual,

No need to mess with the grip.

Loosen the banjo bolt to the brake line first.

The front master slides towards the center of the bike and off after you remove these two bolts, one in the front and one in the back:



Pour some water into the master cylinder piston and let it sit to see if that will dissolve the dried up brake fluid that's holding it in.

moriarti wrote:Hi John ,Removal of master cylinder is what you need to do, you will find out on forum if you dont have a manual,

Thanks for the tip. I thought it was going to be more involved.

Thanks, Duck. Great info and pics. Much appreciated.