Hi all,

Drained the front brake fluid reservoir yesterday, was dripping on fairing covering right side, worried some got on the tank. Washed with a wet sponge a bunch of times hopefully that did the trick. Removed the rubber boot on the piston, ordered a new one. Not sure if that will fix it, every time I pulled the lever it seeped out a bit. Hope the bore isn't worn or I'm replacing the whole package. Not sure if anyone has had the same trouble but I'm hoping a boot is all I need.

Also noticed the screw/bush that hold the front lever do not unscrew with an Allen Key, figured I might need to remove it to replace the new rubber boot once it arrives, am I missing something?

Cheers and thanks for the help.

Chris

yes tsbt ....there is a small seal around the shaft as it enters the cylinder ...more or less at the brake lever to piston junction of the housing where the shaft goes into the cylinder ....this is often the little blighter that needs changing .

the only way i know how to get it is with the "refurbish kit " which contains the piston, main seals and the little one i have mentioned .

worth doing anyhow ....sorry for the bad news ....

but if you find the correct seal and part number as a separate item ...i think we would all be interested to find out

Welcome Chris!

By judging the picture it seems like you got a 4V.

The m/c one these ones has a bit unfortunate design as the outermost piston seal lays very shallow in the bore, and is very often damaged due to corrosion in the outer part of the bore.

About dismantling, have a look in this thread.

Thanks again Inge!

That thread is exactly what I need. Love the detailed photos! So helpful, keep you posted cheers.

Chris

Thanks Charlie, I'll see iff the rubber seals do the trick. I'll look into the refurb too. Whatever I can do the fastest to get this baby back on the road.

Cheers
Chris

Here's what the 20mm master cylinder assembly (for K bikes with four piston Brembo calipers) and bits look like. Order yourself number 20 as well as number 8. It is all-too common with the later masters.



Here is a link to that page.

http://realoem.com/bmw/showparts.do?model=0533&mospid=51709&btnr=32_1969&hg=32&fg=72

Here's the culprit, hopefully some WD40 a flat head and needle nose will do the trick:


Amazing how corrosive this brake fluid is it really ruined the coating.

Thanks again, let you know how it goes.

Cheers
Chris

Yeah, brake fluid is a very effective paint stripper.
But on the other hand, it seems like this m/c have leaked a quite long time.

Good luck, with the bolt!!

Tried everything, and I can't get that screw/bolt out that holds the front lever. It's driving me nuts. I either replace the whole lot which will be expensive obviously, or I take it to a machinist and drill the bolt out and re-thread the hole. Not sure what the best option is, anyone have to do this before? Maybe i'll just bite the bullet. I wanna get this baby back on the roadio.

Cheers and thanks again,
Chris

suport the other side of the casting ....and be carefull how do it ,,,,but get a soft metal (brass maybe ?) punch - drift ...and give the head of the bolt a good whack with a hammer ....drift in between of corse, quite often this breaks the thread seal and in this case the corrosion of the bolt to the housing ...im guessing corrosion and galling is making it rather difficult to start turning ....then with vice grips and an allen key ...(that fits really nice ) attempt to turn it .....it might take another set of hands to hold the assembly whilst you do so ...

just a thought

good luck

Bring it to machinist if you have one in the neighborhood. The problem with cilinder leakage I solve in little hydraulic shop. They ask me to bring whole main cilinder asembly, because they measure the diameter and put exact rubber rings which they produce. Work like that cost me about 15 euros.
I had problem with leakage after mount a steel brake tube. Higher pressure caused the leakage.

Regards

A hammer blow won`t do much good one this one, Charlie.
Would only damage the fine threads in the lever.

By judging the picture the bolt is out of the threads in the lever, and now just turning around.
Normally the screw now should be pulled straight out using a plier....have you tried that?

It is now corrosion in the bore around the split bushing that keeps it back.....
and now that the bolt is this far out the split bushing should be close to the end of the bore.

Have you tried to heat gun yet? the housing would expand more than the bolt and bushing.
You could also try to turn the screw back in and the out again a few times, and with this moving the split bushing up and down the bore and releasing some more of the corrosion, use enough penetrating oil.......try a 50/50 mix of acetone and ATF.

good to have first hand knowledge inge ...cheers !!!

charlie99 wrote:good to have first hand knowledge inge ...cheers !!!

Sometimes it ain`t easy to know how things are put together, without done it yourself a couple of times.

And this bolt/lever assy is quite different from normal....2V.

Lesson learned: get a vice and a good, large pair of vice grips. Oh and have a super helpful, trustworthy, BMW mechanic to ask questions to when you're stuck.

Took the MC to my BMW mechanic friend Chuck Stryker, one of the only guys in Toronto that fixes old BMW's - worked for them for something like 20years before starting his own shop, I think he's close to 70. I look for any excuse I can to swing by his garage for shop-talk and to pester him for an apprenticeship, hopefully one day he'll take me up on it.

Anyway he put a good pair of vice grips on the bolt, put them in a vice and gave it the MC a smack and the thing slid out, like a hand from a glove. The reason it wasn't screwing all the way was, as suspected, the thread was stripped right near the top of the lever. He sold me another MC for $60 which I installed yesterday and thanks to some of his bleeding tips and Inge's link, I'm a happy man.

Only thing left to do is move the throttle/MC assembly up the handlebar more, when I tightened the nut at the end of the bar it must've pinched the throttle because it didn't move. Today's project. That and hopefully take it for a ride!

Thanks everybody.
Chris