GL1100 rear break master cylinder volumes


Information and questions on GL1100 Goldwings (1980-1983)
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ontheside
Posts: 7
Joined: Sun Aug 20, 2017 6:53 am
Location: France
Motorcycle: 1980 GL1100 fitted with 1985 EML sidecar and Squire Trailer

GL1100 rear break master cylinder volumes

Post by ontheside »



After 37 years of owning a GL1100 I have discovered Goldwing Docs - well better late than never. I have a question about the rear brake master cylinder fluid volumes. I am aware that the 1980 and 1983 have slightly different master cylinder characteristics mainly I believe to serve the twin piston / linked brakes on the 83 model. However I have recently bought a renovation kit for the 1980 master cylinder and was sent the 83 kit by mistake. I have since bought an 80 kit from the US and its fine. Other than a small difference to the internal spring length and what I will describe as a 'spiral' piston (which is the same length and diameter as the 1980 piston) the renovation kit appears identical to the 80. Maybe there are also differences in the main master cylinder body but I do not have an 83 to compare.

The reason I ask is that I have an EML sidecar on the GL1100 and that is fitted with a small disc, currently both the GL1100 rear single piston disc and the EML sidecar disc are powered by the 1980 master cylinder. The pedal travel is greater than original due to the introduction of the additional disc. If the later 1983 master cylinder 'moves' more fluid this may reduce the brake pedal travel? I cannot however see how the 83 will move more fluid as length/diameter is same but maybe someone can enlighten me?

Note: I have had this setup for more than 35 years covering countless miles all over Europe and it works fine but convincing the test centre technician that it works fine is getting a little tedious!


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jeffcosmo
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Location: Burlington, WI (Honey Lake)
Motorcycle: 1983 GL1100 Aspencade
1983 GL1100 Aspencade
1983 GL1100 Aspencade (parts bike)

Re: GL1100 rear break master cylinder volumes

Post by jeffcosmo »

I DO have a couple '83 master cylinders, will be able to check diameter in the morning.

However, '83 rear calipers are different, and that may be the difference (a difference in piston diameter allowing for the actuation of the front caliper, which is also different from earlier GL's).

You may have better luck putting an '83 caliper on, than finding a master with a larger diameter piston.

Cosmo
ontheside
Posts: 7
Joined: Sun Aug 20, 2017 6:53 am
Location: France
Motorcycle: 1980 GL1100 fitted with 1985 EML sidecar and Squire Trailer

Re: GL1100 rear break master cylinder volumes

Post by ontheside »

Thanks for the information, I have no knowledge of working on the 83 1100 setup other than I know its different - linked brakes and twin piston calipers. The piston from the 83 renovation kit looks a similar diameter although I have not put a micrometer on it, a very small increase that may not be visible to the eye immediately may be sufficient to increase fluid volumes to the brakes? I will micrometer both and see!

Thanks

on the side France
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