Need advice on front master cylinder rebuild

Information and questions on GL1000 Goldwings (1975-1979)
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1975 GL1000

Need advice on front master cylinder rebuild

Post by bbuice » Fri Jan 21, 2011 10:49 pm

Hi Everyone. I am working on restoring a 1975 GL1000 and am working on the brakes. I am having a problem with the front. I rebuilt the calipers, put on new stainless hoses a couple of weeks ago. Just rebuilt the front master cylinder using a new rebuild kit and put a new reservoir cup on it. I put it all together tonight and started bleeding the brakes. I got fluid out both bleeders. But, the brakes won't "pressurize". When I closed the bleeders and squeeze the brake lever it will never firm up. It just pumps and pumps. I even tried putting a bolt in the outlet side where the banjo goes and it won't make much pressure that way. It will get stiff but I would think that you should be able to get complete resistance at the lever that way. I pulled it all back off and took it apart again but everything looks fine to me.

Any suggestions would be much appreciated.


Benny Buice
Marietta, GA
1975 GL1000
2003 GL1800

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Re: Need advice on front master cylinder rebuild

Post by WingAdmin » Sat Jan 22, 2011 11:20 am

When you put the new rubber washer on the piston, did you put it facing the right way? If it's on the wrong way, it will not pressurize the brakes.

Picture taken from a GL1100, but similar on GL1000:


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Re: Need advice on front master cylinder rebuild

Post by thrasherg » Sat Jan 22, 2011 9:50 pm

Sounds like you might still have air in the system. I was told a trick many years ago that has worked many times for me.. Bleed the system as best you can, then quickly pump the brake lever to get as much pressure as you can then cable tie the brake lever back to the handlebar and leave the system pressurised overnight.

Any air that is trapped in the system will be compressed (so the bubbles become smaller) and will have an easier time rising up the brake lines. it is also recomended to tap the banjo's and lines to try and free up any air bubbles.. turn the handlebars so the master cylinder and reservoir are at the highest point, I have always found that if I leave the system pressurised overnight like this, I will get some air bubbles the next day when I remove the cable tie and the brake system works much better. I always have more issues getting the air out of new brake lines than old ones (Don't know why!!). Worth a try to see if it helps your system. Also it sometimes helps to force the brake pads back into the calipers, this pushes brake fluid up the lines to the master cylinder and this will often bring any trapped air with the fluid.


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Re: Need advice on front master cylinder rebuild

Post by raycw » Sat Feb 12, 2011 2:42 pm

any luck getting the brakes to pressurize??

One note that might be a little late: When bleeding any front brake system it's NOT a good idea to pull the lever all the way back to the grip. The reason being is that the cup (shown in the picture) can travel past the relief holes in the master cylinder and can nip a piece out of the rubber cup. That could allow fluid to weep past it.

I tie a rag around the grip and double knot it facing forward so the lever hits the knot and doesn't hit the grip. That trick was shown to me at the Honda Tech school I attended back in the early 70's.

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