on my 85 k100RT between the adjuster stud and plunger for the rear master is a rubber peg with a washer vulcanized to it. it has sheared off about a 1/8 " from the top. looks like it gives some nice gradual/soft type feel to the rear brake. don't want to buy the $65 master rebuild kit for this piece. anybody tried something different in there ? plastic tubing, fuel line,vacuum line etc. looks like you need the button washer on top to mate with the rounded adjuster peg when done...
maybe something harder or firmer would give the rear brake a better feel too. tried to drill a hole in the rubber of both halves and put a small stud in there but there just isn't enough material on the washer end left to do anything with.

if someone was handy with a lathe ...wouldn't be hard to turn something up
I think sidecar paul has already done this

might be a good idea to use the search feature to find the article again ??

i'm going to take a small bolt, put some O rings on the outside of it to isolate it from the bore, give it a dish shape on top with a large drill bit, put a piece of rubber down in the base of the MC piston to give it some cushion and then cut it to length.
the original kinda looks like a tire plug with a dished washer vulcanized to the top of it. sure is a lot of rubber there to give the pedal a cushy feel. you can see it in the bottom left of my pic.

I am not 100% sure on this but I think it's what is called a reaction pad and is used in power boosters on cars.
It prevents a very sudden jar when the brake is applied and may be there to help overcome the jar for the sake of the ABS models.  No guarantees just my thoughts on it.

i agree with your logic.
no abs here. being the rear i believe it helps with not locking up the wheel.
gives it more of a gradual apply. i used a drill bit to dish the head of a bolt to copy the washer that was on top of the rubber plug. slid some silicone tubing on it to isolate it from the MC bore. threaded a hard faucet washer on it to give it that cushion between it and MC piston. works well and i'm confident it will stand the test of time. the original sure has a lot of rubber there to do a lot of flexing side to side eventually failing. it only lasted 29yrs.....

Only 29 years!!!   take it back if you have the receipt. 

he did have a 2yr rest in a barn. i'll call him "Grumpy"
i found him up by the NH border. cut a deal with the owner and had to wait about 6 weeks till the snow in his yard melted enough to get him out. he used windshield washer to un freeze the barn door. that was a looooong anxious 6 weeks. i spent a few weeks on cleaning all connections and grounds, changing all fluids, clutch and diff spline lubes, fork gaiters, intake boots etc etc etc. the past month i have put an enjoyable 2k miles on him. he was still a youngster when i found him with only 25k. got 27k now and counting. if i can stop riding him long enough i still have some new fork springs and SS brake lines to install.

I did try making a solid fitting to replace the rubber block but it made the brake into an 'on/off' switch.  

Ultimately, I added a spacer, about 3mm, over the rubber to reduce the squidge but still retain some feel.

Paul.


https://www.k100-forum.com/t3739-mod-to-rear-brake

i did the opposite but same effect.
made a metal peg similar to your's but with a rubber washer between it and the master..
you used the original rubber peg with a metal washer.
my bike came with some new spare parts including the master rebuild kit minus the rubber peg.....
BMW does not sell the peg separate.
my original sheared off. the original has a bunch of rubber sticking out to compress.
we both reduced that amount of rubber to squish
works well now with great "feel"