'81 GL1100 front brake master cylinder replacement part


Information and questions on GL1100 Goldwings (1980-1983)
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hondaazz
Posts: 10
Joined: Fri Jul 19, 2019 5:51 pm
Location: RI, United States
Motorcycle: 1981 GL1100I
1978 CB400TII

'81 GL1100 front brake master cylinder replacement part

Post by hondaazz »



I'm having a tough time with this master cylinder. I had to replace the reservoir due to the original being weathered and warped and replacing the rubber gasket wasn't enough. I then rebuilt the piston assembly, but now the spring appears to not be strong enough to return the lever back to "home" and this keeps my brake light on. The rebuild kit was from eBay, so that could be problem #1. Disconnecting the light switch is only a temporary fix.

However, I do not care for the "split reservoir" design because of the added failure point - and cost - of the plastic reservoir. I have heard somewhere that there has been some success with using a master cylinder off of a ST1100 since that too has the dual caliper assembly. Can anyone either back that claim up before I make the purchase, or suggest a better alternative to a one-piece master cylinder?

BTW, I also had to rebuild the rear master cylinder (also using eBay as a parts source) and have had 100% success with that project.


hondaazz
Posts: 10
Joined: Fri Jul 19, 2019 5:51 pm
Location: RI, United States
Motorcycle: 1981 GL1100I
1978 CB400TII

Re: '81 GL1100 front brake master cylinder replacement part

Post by hondaazz »

For anyone who may be interested in replacing the '81 front master cylinder, I would strongly recommend the ST1100 master cylinder as a drop-in replacement. It's a single piece with a sightglass that faces you, and the handle is adjustable for those with big hands. It bolts right up to 7/8" bars, and of course has the built-in brake light switch. I bought mine used and have no complaints. It may even be cheaper than rebuilding the original - the replacement plastic reservoir is $40-$50 alone.
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newday777
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Joined: Tue Jan 11, 2011 5:21 pm
Location: Milford NH summer/fall & Oceanside, CA winters(N San Diego) with lots of miles riden between
Motorcycle: 2008 Cabernet Red. Level 4

1983 GL1100A Wineberry 36,000 miles

1975 CB750 K5 Planet Blue 7,800 miles

1976 CB750 K6 Anterris Red 25,000 miles

Past rides
1999A Restored from PO neglect & sold at 19,000 miles

1999SE Totaled by cager at 105,000 miles

Re: '81 GL1100 front brake master cylinder replacement part

Post by newday777 »

hondaazz wrote: Sun May 24, 2020 8:25 pm For anyone who may be interested in replacing the '81 front master cylinder, I would strongly recommend the ST1100 master cylinder as a drop-in replacement. It's a single piece with a sightglass that faces you, and the handle is adjustable for those with big hands. It bolts right up to 7/8" bars, and of course has the built-in brake light switch. I bought mine used and have no complaints. It may even be cheaper than rebuilding the original - the replacement plastic reservoir is $40-$50 alone.
The 81 GL1100 came with single pot calipers.
The ST1100 came with double pot calipers and will have a larger diameter bore master cylinder and might give you problems.

https://www.onallcylinders.com/2013/10/ ... s-braking/
hondaazz
Posts: 10
Joined: Fri Jul 19, 2019 5:51 pm
Location: RI, United States
Motorcycle: 1981 GL1100I
1978 CB400TII

Re: '81 GL1100 front brake master cylinder replacement part

Post by hondaazz »

It does not appear to be a concern to me in this situation. I've run the bike and I'm not seeing any issues with stopping. If someone also wants to change their front brake master cylinder and post their results here, I'd be interested to see their results too. IMHO, this is a more cheaper, reliable upgrade to the goldwing.


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