Author Topic: Rebuilding Master Cylinder  (Read 337 times)

Offline MikeFossl

  • Posts: 72
Rebuilding Master Cylinder
« on: September 11, 2020, 10:13:32 AM »
Any gotcha’s?   Is there a step by step somewhere on the forum?

Thanks!
1985 R65


Offline dogshome

  • Posts: 116
Re: Rebuilding Master Cylinder
« Reply #2 on: September 11, 2020, 02:03:49 PM »
Very easy job. I would add that putting a micro drill or other very fine wire through the return bleed port is a good idea. A sewing pin is too large. Also to lubricate the dry side where the circlip is with brake friendly grease. The stuff that comes with caliper rebuild kits. That area suffers corrosion.

If you keep the fluid in the lines, bleeding should be fairly easy. You will see bubbles rise from the bleed hole with the reservoir cap off.
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline BPT

  • Posts: 718
  • I Love YaBB 2!
Re: Rebuilding Master Cylinder
« Reply #3 on: September 12, 2020, 07:33:12 PM »
Would that be the recommended way (easiest and most efficient) to bleed the brakes? I've always had help in the past but need to do it solo.  Seems there's almost as many opinions on how to do that as there are oil posts on Airhead forums.
I've heard good and bad about using a device or not,  top to bottom or  vice versa, etc., etc.  One of those questions I'd been wanting to  ask but have put it off.  Not sure why I dread brake bleeding, but I do.......
1983 R65 w/ Velorex 562 Sidecar

Offline wilcom

  • Posts: 1485
Re: Rebuilding Master Cylinder
« Reply #4 on: September 12, 2020, 08:55:55 PM »
Quote
Not sure why I dread brake bleeding, but I do.......

Because it is a PITA ;D that's why. I've done it top to bottom and bottom to to-top used a vacuum pump. I just go back to the ol fashion way. The MC is so small it takes forever to bleed them, just stick with it and make sure that lil return hole is free and clean, the one you use the piece of small wire to poke thru. I had mine bled and a hard grip in about 10 minutes the last time I did mine. I have also cussed them for an hour to get the same job done. I haven't a clue as to what I'm doing differently when I have success?

Good Luck
Joe Wilkerson
Telephone man with a splash of Data
Menifee, CA

Present:
1984 BMW R65LS "Herr Head"
1982 BMW R65LS 
past:
1979 R65
1980 R65
1982 R80RT
1974 R90/6
1972 R75
1964 R50/2
19xx R27
ZX-11

Offline BPT

  • Posts: 718
  • I Love YaBB 2!
Re: Rebuilding Master Cylinder
« Reply #5 on: September 12, 2020, 09:46:52 PM »
Haha, thanks, I don't feel so bad now. I thought i must be missing some small thing or just never had that "A-Ha!" moment where it all became clear.  I guess I'll try it the basic way like in your video link, and hope for good luck.
1983 R65 w/ Velorex 562 Sidecar

Offline dogshome

  • Posts: 116
Re: Rebuilding Master Cylinder
« Reply #6 on: September 13, 2020, 02:10:26 PM »
Mine was fine, just patience. Do one side, then the other and be prepared to do the first then second sides again. A clear bleed hole makes the difference,
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline BPT

  • Posts: 718
  • I Love YaBB 2!
Re: Rebuilding Master Cylinder
« Reply #7 on: September 14, 2020, 01:36:14 AM »
Well I only have a single disc so at least it'll only suck half as much ??
1983 R65 w/ Velorex 562 Sidecar

Offline Barry

  • Posts: 5014
Re: Rebuilding Master Cylinder
« Reply #8 on: September 14, 2020, 10:04:40 AM »
If it's only a routine fluid change then the easiest fool proof way is to gravity bleed.  Just attached a short length of tube, open the bleed nipple and let it drip into a jar.  As long as the reservoir is kept topped up it's impossible to introduce air. No fuss and a solid brake lever every time.
Barry Cheshire, England 79 R45

Offline BPT

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Re: Rebuilding Master Cylinder
« Reply #9 on: September 15, 2020, 04:11:21 PM »
Thanks Barry.  I need to do it soon so I'll give that simple method a shot.  Maybe the stars will be aligned correctly and it'll work for me.
        Thanks
1983 R65 w/ Velorex 562 Sidecar

Offline skippyc

  • Posts: 339
  • Shouldn't have sold them old bikes.
Re: Rebuilding Master Cylinder
« Reply #10 on: September 15, 2020, 05:51:44 PM »
I have 2 cheap one way valves with pipe on each end. I can plug them on to the bleader valves and pump the fluid through. takes no time at all.
I think the valve were fuel valve, ebay specials.