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I am rebuilding/customizing a GL1100 and have been working through a long list of issues but one of the more frustrating has been the rear brake master cylinder. I have three now and although perhaps it is a reflection of my skill level I have not been able to get any of them to work properly. Since these parts are now 30+ years old and often left unused for decades they are often thoroughly gunked up to say the least.

I decided to look for something newer that could be substituted and decided to try the GL1800 series since they are only a few years old and plentiful and often cheap. I bought a nice clean one from a 2009 bike complete with hydraulic fluid for $35 including shipping. Less than the price of a rebuild kit.

It turns out the conversion is quite simple. The GL1800 has a slightly larger piston and the mounting tabs are in different locations and the threaded shaft must be cut down but a reasonably skilled person with ordinary hand tools can make an adapter and install the new master cylinder in a couple of hours. Some hand fitting is required and this gets tedious with a fully assembled bike.

After a test ride through town today, I am quite satisfied with the function and do not feel the larger piston/cylinder will create any problems.

Unfortunately, I forgot to photograph the reservoir in place but it is unchanged from the original configuration. The GL1800 hose is about a 1/2 inch shorter but the mounting adapter on the cylinder itself is long enough that the tube can be slid off a bit to create more length. The original GL1100 reservoir must be used since the mounting angle is different for the GL1800 and the tube comes out of the side rather than the bottom as on the 1100. It is also smaller in diameter but I was able to push the 1100 reservoir onto the tube without much trouble. A larger clamp is required so put it on first or you will be taking it back apart as I did!

It was relatively easy to prime. I left the banjo bolt loose until I had fluid seeping out, then tightened it and opened the bleeder valve at the caliper. A small tube placed over the bleeder valve goes into a can of brake fluid to prevent suction from pulling air back into the line. In a few minutes I had the brake bled and was ready for a ride. After a few miles warming up the pads and seating them, the rear brake felt just fine.

nice job

Good to know. Nice work.

Good info, thanks.

Useful to know for when the time comes.

Hey Easter,

You have had some time to test ride and get a good under standing as to the Pro's & Cons, of going to this conversion.

1. Do you get any brake lockup, Front or Rear?
2. What about panic stop, can you lock either wheel larger piston means more brake power?
3. Any problems that you have encountered?
4. How does the foot brake feel now? any excess foot pedal play?
5. Are the brake similar to the way they were stock?

I have a 1983' GL1100 with linked brakes That i will be testing this on.

Easter wrote:I am rebuilding/customizing a GL1100 and have been working through a long list of issues but one of the more frustrating has been the rear brake master cylinder. I have three now and although perhaps it is a reflection of my skill level I have not been able to get any of them to work properly. Since these parts are now 30+ years old and often left unused for decades they are often thoroughly gunked up to say the least.

I decided to look for something newer that could be substituted and decided to try the GL1800 series since they are only a few years old and plentiful and often cheap. I bought a nice clean one from a 2009 bike complete with hydraulic fluid for $35 including shipping. Less than the price of a rebuild kit.

It turns out the conversion is quite simple. The GL1800 has a slightly larger piston and the mounting tabs are in different locations and the threaded shaft must be cut down but a reasonably skilled person with ordinary hand tools can make an adapter and install the new master cylinder in a couple of hours. Some hand fitting is required and this gets tedious with a fully assembled bike.

After a test ride through town today, I am quite satisfied with the function and do not feel the larger piston/cylinder will create any problems.

Wish I'd come across this post before spending months and $125+ hunting down an original that only took 5 days of soaking to get the circlip and washer out so I could start on the old frozen piston... .

westgl wrote:Hey Easter,

You have had some time to test ride and get a good under standing as to the Pro's & Cons, of going to this conversion.

1. Do you get any brake lockup, Front or Rear?
2. What about panic stop, can you lock either wheel larger piston means more brake power?
3. Any problems that you have encountered?
4. How does the foot brake feel now? any excess foot pedal play?
5. Are the brake similar to the way they were stock?

I'm curious about these, too. How's it working out, Easter?

Nice write up if I can work it in I may have to do this since I am in the middle of a build.

I just did this...took about an hour and works great. Used a master from a 2001 gl1800 same as pictured in this thread.

I never rode with stock brakes so I cant compare the feel, but its pretty close to what my sportbike is like. If not better. I wish I would've just done this instead of hunting down a second M/C...cost about the same as a rebuild kit.


Pics in my build thread.

Easter wrote:I am rebuilding/customizing a GL1100 and have been working through a long list of issues but one of the more frustrating has been the rear brake master cylinder.

what year 1100?

i know of one (& only) other recent 83 conversion that i don't think has been tested much, comments are in this thread

I just did this...took about an hour and works great. Used a master from a 2001 gl1800 same as pictured in this thread.

I never rode with stock brakes so I cant compare the feel, but its pretty close to what my sportbike is like. If not better. I wish I would've just done this instead of hunting down a second M/C...cost about the same as a rebuild kit.

Pics in my build thread.

http://ngwclub.com/forum/viewtopic.php?p=562670#p562670

westgl wrote:Hey Easter,

You have had some time to test ride and get a good under standing as to the Pro's & Cons, of going to this conversion.

1. Do you get any brake lockup, Front or Rear?
2. What about panic stop, can you lock either wheel larger piston means more brake power?
3. Any problems that you have encountered?
4. How does the foot brake feel now? any excess foot pedal play?
5. Are the brake similar to the way they were stock?

I have a 1983' GL1100 with linked brakes That i will be testing this on.

Easter wrote:I am rebuilding/customizing a GL1100 and have been working through a long list of issues but one of the more frustrating has been the rear brake master cylinder. I have three now and although perhaps it is a reflection of my skill level I have not been able to get any of them to work properly. Since these parts are now 30+ years old and often left unused for decades they are often thoroughly gunked up to say the least.

I decided to look for something newer that could be substituted and decided to try the GL1800 series since they are only a few years old and plentiful and often cheap. I bought a nice clean one from a 2009 bike complete with hydraulic fluid for $35 including shipping. Less than the price of a rebuild kit.

It turns out the conversion is quite simple. The GL1800 has a slightly larger piston and the mounting tabs are in different locations and the threaded shaft must be cut down but a reasonably skilled person with ordinary hand tools can make an adapter and install the new master cylinder in a couple of hours. Some hand fitting is required and this gets tedious with a fully assembled bike.

After a test ride through town today, I am quite satisfied with the function and do not feel the larger piston/cylinder will create any problems.

Ok so I got an 1800 master cylinder and want to do this swap/upgrade. But the hard line that goes in to the 1100 rear master on my 83 has a line nut on it. How do I swap it to a banjo fitting? I'm guessing I cut the hard line and slip a rubber brake line with a banjo fitting on the end end, over the hard line and secure with a clamp of some type??

Well I just checked a couple places here in town and they said they can't do it. Don't have the banjo fitting. NAPA said they can't crimp the fittings to the lines, a DOT thing.

I'm not a fan of clamps on brake line fittings. I would have a new line made, with the correct ends

Found a couple on line places. Guess I'll get it done but thought it would be a little quicker swap. Shoulda checked it out a little more first.