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Old 04-06-2011, 09:19 AM   #1
davemon OP
High Speed Airhead
Joined: Jun 2007
Location: NC
Oddometer: 124
Airhead Rear Disc brakes

I realize the brakes on the airhead leave a lot to be desired but anyone figured out how to make the rear disc on a 77 R100S work? Caliper change?
Master cylinder change? Mine won't lock the rear wheel if I stood on it with both feet. Not really willing to go to drum but looking for a fix.
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Old 04-06-2011, 11:47 AM   #2
Hawk Medicine
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77 R100S with a rear disc?

The "S" bikes were manufactured with drum rear brakes.

Hate rots the pocket that carries it.
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Old 04-06-2011, 01:01 PM   #3
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Originally Posted by mymindsok View Post
77 R100S with a rear disc?

The "S" bikes were manufactured with drum rear brakes.
Until 78.
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Old 04-06-2011, 07:53 PM   #4
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It is a REAL job to get all the air out of that system. I suspect that is your problem. That and/or a shot rubber line.
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Old 04-06-2011, 07:57 PM   #5
Boxer Metal
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It could have been made from 9/77-12/77. The only way to get the rear disc to work is a smaller bore master cylinder like a 12mm. Modify the mounting to use an earlier K100 with ABS, R1100 or R1150 rear brake master cylinder.
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Old 04-06-2011, 08:05 PM   #6
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New brake hose is a must on these old Airheads. The originals have all swelled up and choked the hole down the centre by now.

And that rear brake is a bitch to bleed for some reason. Taking caliper off and hanging it so rubber hose is vertical helps, as does a vacuum bleeder.

Can't remember exactly but I think there were two sizes of master cyl bore, the later ones being smaller and more effective. You can get the old ones sleeved to fit the later piston/seal.
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