1979 R65 brake problem

schrader7032 · Post by **schrader7032** » Thu Jan 28, 2010 4:52 pm

Jim -

Is this for an under-the-tank master cylinder? I believe it should be unless it's been changed. On my '78 /7, there's supposed to be the ability to adjust the position of the master cylinder piston in the bore by turning the adjuster knobs at the rear of the master cylinder. There is supposed to be a special "forked" tool that fits into the groove to identify the depth. I believe I just eyeballed it with a ruler. This should result in about 0.2-0.25" free play at the hand lever. After that, full brake action is dependent on the internals of the master cylinder piston, brake bleeding, etc.

Are you saying this master cylinder has no adjustment like mentioned above? The above is basically what is in my Haynes for bikes up through 1980.

Beyond that, I'm not sure what else to suggest.

Kurt in S.A.

Darryl.Richman · Post by **Darryl.Richman** » Thu Jan 28, 2010 8:46 pm

Curious topic; I've just gotten an '81 R65 running, and the brake lever comes to maybe 1/2" from the bar before the brakes come on. They work correctly otherwise. I've already bled them and they act the same.

I believe that there are more than 2 possible MCs, although I don't think the R65 ever came with an under-tank MC. Correct me if I'm wrong, but I believe that the '79 and '80 bikes had a round MC, while the '81-'84 bikes had the rectangular MC. And there are two different bores on each, for single and dual disks (which were an option on the R65 and stock on the R65LS).

I haven't had a chance to do any research into this topic beyond what my (probably wrong) memory says.

schrader7032 · Post by **schrader7032** » Fri Jan 29, 2010 7:52 am

I guess my Haynes is wrong or I misinterpreted it. I checked the ETK listing for a '79 and the picture shows a round master cylinder while the picture for an '82 has the square one. As much as you can trust those images, that seems to be the case.

Kurt in S.A.

jimstravlin · Post by **jimstravlin** » Sat Jan 30, 2010 8:14 am

the culprit in question is the front brake and the master cylinder is on the handlebar. yes there are two different plungers for the dual disk and the single disk and we have the correct plunger in the MC. it almost seems that the rod on the plunger is too long and does not allow any slack in the pull on the handle. actually when you put the lever with the plunger into the MC you have to push it in and you are applying pressure on the rod right away. there seems to be no obstructions in the cylinder where the plunger lever goes. it is the strangest thing...thanks for your help.....jim

VBMWMO · Post by **VBMWMO** » Mon Feb 15, 2010 2:53 pm

we have a 1979 R65 in the shop with a front brake problem. the brake is great but has no distance on the lever pull till the brake is on full. the amount of pull is probably 1/2 - 3/4" at which time the brake is on full. the master cylinder has been rebuilt and it is clean and beautiful inside. i am aware that there are two possible plunger shafts, one for up to 1980 and the other 1980 on. we have put in the correct plunger. there is no adjustment on that model. thought the shaft on the plunger may be too long and looked at the other and only difference is larger diameter, shaft length the same. has anyone encountered this problem???? .... thanks.... jim

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