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Master Cylinder rebuild 78 R100/7

SCBuckeye

New member
Any advice or help on rebuilding the brake master cylinder on my 78 R100/7? I ordered the kit, should be here today, for the 14mm cylinder (I have a single brake rotor).

Any videos/articles out there?

What should i NOT do?

Thanks in advance.
 
Jim: It is a straight forward job for anybody with a little mechanical experience around motorcycles (which i know you have!), which does not require much instruction. Don't spill any breakfluid on the frame or other painted parts.
 
I just finished this on a cylinder that had been sitting for several years. Someone has a very good tip about using dental floss to install the captive seal on the piston. I cannot remember where I read it but maybe someone else knows.
 
Jimmy,

Here's a picture link to my rebuild of the M/C recently. I would throw in an additional suggestion with the addition of an old caulk gun tip cut to length for the assembly of the rubber cup on the piston spool. Works a charm. Good luck with the rebuild.

http://tinyurl.com/by4b8pj



-Mike V. / San Diego
 

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  • 78R1007 MC Rebuild 04-09-11 002small.jpg
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WOW again!

You guys are great!!

I had forgotten that dental floss trick, and using the calking tube tip is really neat.

I plan on doing this starting early Sat. morning.

The advice about the brake fluid and paint is good.

Mike, did I once hear you say to use DOT 4 and NOT DOT 5?

Thanks again to all of you.

I am amazed at how easy it is now to get great first-hand advice from first hand mechanics and also from some of you old geezers than it used to be when I was a member some 25 to 30 years ago.

Its like having a wealth of knowledge right here at my fingertips.
 
Jimmy,

Dot 3 or 4. Preferably Dot 4. Not the Dot 5 Silicone base. Be sure to change it annually. You know it's hygroscopic and absorbs ambient moisture which is cancerous for our brake's internal organs. Dot 4 has a higher boiling point - not that we need to concern ourselves so much about that for normal riding habits.

Remember the key to M/C and Caliper rebuilds is; clean, clean. clean.

-Mike V.
 
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Jimmy,

Here's a picture link to my rebuild of the M/C recently. I would throw in an additional suggestion with the addition of an old caulk gun tip cut to length for the assembly of the rubber cup on the piston spool. Works a charm. Good luck with the rebuild.

http://tinyurl.com/by4b8pj



-Mike V. / San Diego

Excellent documentation. Thank you.
 
R100/7 Master Cylinder Rebuild...

Hey all! I'm doing a similar job. Having real trouble locating the rebuild kit. BMW has apparently discontinued it. The bike I'm working on has a single front caliper and a 14mm master cylinder piston diameter. Great tip on the caulking tip...

If anyone has a lead on where to buy the rebuild kit, please let me know!

<edit>
I found a rebuild kit at Euro Moto Electrics!

Excellent documentation. Thank you.
 
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I did my /7 master cylinder three years ago...I bought my parts from the dealer. Guess things change over time. You could try Tom Cutter at Rubber Chicken Racing Garage, Ted Porter at Beemershop, or Anton Largiader at Virginia Motorrad Werkstatt. There are European options as well...Motobins seems to have a kit on their website https://www.motobins.co.uk/
 
Only time

It is pretty easy to rebuild the MC, the only time a problem crops up is if the bore is pitted. Even if that is the case, there are companies who re sleeve them. St.
 
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