Any help 4 my 82's rear master cylinder issue?


Information and questions on GL1100 Goldwings (1980-1983)
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rodee71
Posts: 84
Joined: Mon May 14, 2012 1:18 pm
Location: Winchester, Virginia
Motorcycle: 1982 1100 Interstate
1993 1500 Aspencade

Any help 4 my 82's rear master cylinder issue?

Postby rodee71 » Fri Jul 13, 2012 7:44 am



I rebuilt the rear master cylinder with a new kit on my 82 Interstate. Before rebuilding it, I rebuilt the caliper with a new kit, but the brakes would lock up if I used them. The first thing I did before I rebuilt the master cylinder was take a wire and clean out the pinhole in the one chamber, clean it up, and reinstall it. They worked fine for 2 days and then locked up tight on the rotor. So I rebuilt the cylinder completely, cleaning out the pinhole again (saw nothing actually coming out the pinhole). Now, even after I pumped fluid into the reservoir line all the way thru the system and out the caliper bleeder screw with a small (new) vacuum pump in order to fill the system, they will not pump up when I try to bleed the system. No resistance whatsoever. Of course, I used the how-to from the site to do the rebuild. My cylinder walls look fine, no scratches that would allow fluid to by-pass the seals and the footbrake pedal did pump the fluid thru and out the bleeder when it was under pressure from the vacuum pump, so I assume the system is full of fluid. I'm at a loss as to what I missed or is there someone who might have a solution?
BTW, great site and nice people. What a good place this is for us Wingers with problems to go for info. Any Ideas?



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dingdong
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Re: Any help 4 my 82's rear master cylinder issue?

Postby dingdong » Fri Jul 13, 2012 7:51 am

Well it sounds like you have done everything correctly so I don't have a definite solution. There is one possibility though. It is possible to install the rubber cup/cups backwards which would keep the master from operating properly under pressure. ????
Tom

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rodee71
Posts: 84
Joined: Mon May 14, 2012 1:18 pm
Location: Winchester, Virginia
Motorcycle: 1982 1100 Interstate
1993 1500 Aspencade

Re: Any help 4 my 82's rear master cylinder issue?

Postby rodee71 » Fri Jul 13, 2012 8:03 am

Thanks for the reply, Dingdong. There are two rubber seals, one that mounts on top of the spring, which actually wraps over the spring and has a small tit that fits into a matching hole in the cap on the spring, which could only go back on that way. The other is the one that sits on top of the metal plunger that goes in on top of the spring. This plunger has a crown on the top of it that is concave and accepts the rod from the brake pedal. The seal has to be installed over this crown into the groove in the plunger. Of course, I was carefu to use liberal amounts of fluid in oreder to slide the seal over the crown of the plunger and made sure it was wiping tin the correct direction. I examined the seal very closely after installation to confirm that it wasn't damaged by the extreme amount of stretching it took to slide over the pluger and into the groove. So, I don't know.......

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WingAdmin
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Re: Any help 4 my 82's rear master cylinder issue?

Postby WingAdmin » Fri Jul 13, 2012 5:26 pm

I agree with dingdong - the master cylinder is not that complex a device, just a pump with a couple seals and a return hole. What about drawing fluid through with the vacuum pump WHILE pumping the rear brake downward (then hold it, close bleed nipple, and release brake pedal)? The only possibilities I can think of are a seal problem in the M/C, or a stubborn air bubble that isn't being worked out somehow.

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rodee71
Posts: 84
Joined: Mon May 14, 2012 1:18 pm
Location: Winchester, Virginia
Motorcycle: 1982 1100 Interstate
1993 1500 Aspencade

Re: Any help 4 my 82's rear master cylinder issue?

Postby rodee71 » Sat Jul 14, 2012 12:12 am

Hi Wingman thanks for answering, I did push the fluid thru earlier, but I will try pulling it thru like you said. Here's hoping.o




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