1100E Master Cylinder Rebuild

[Turtleface]

Well, got the front calipers rebuilt, along with the front master cylinder. Slapped on the new stainless lines, topped off the reservoir with fresh brake fluid, and attempted to bleed the brakes. Cracked the bleeder on the left caliper, got nothing. Tried the right caliper, nothing. Pulled the line off at the MC, I get no fluid out the banjo bolt port when the lever is pulled. Fluid does emerge from the weep hole on the bottom of the caliper, but not with any force. This is how I put everything back together:



Did I miss an o-ring or something? Did I install the parts in the wrong order? Can't work on making the bike go until I can make the bike stop. Though I did get a shiny new top end oiler that I can install in the interim.

[Colin Green]

My GS1100G has the same MC but my piston is different and I don't have the extra washer... See pic.

I made up a 3 mm spacer to take out the dead space between the seal and the smallest hole. Reduces wasted lever travel from approx 30 to about 10%.

It does take a lot of lever compressions to work the fluid into the piston bore in the MC. Look for little bubbles coming out of the smallest of the two holes in the bottom of the MC. I found it took literally hundreds of mini strokes just to load up the MC and dozens of full strokes to prime the new lines. May as well fit bleed hoses to both calipers and crack them open while you pump the initial loads of fluid through. Keep the lid off (fit a bit of cling wrap over with a rubber band) and keep topping it up with a syringe.

[hikermikem]

Isn't there supposed to be a cup seal on the piston shaft ??

[Turtleface]

Isn't there supposed to be a cup seal on the piston shaft ??

This is, to the best of my recollection, all the internals. Every piece shown is new Suzuki OEM. #1 goes into the the bore of the master cylinder, with the cup facing outwards. #2 is a thin brass? washer. I'm not terribly certain it goes where I have it located. #3 is the piston, it goes in with the flat, round side facing the cup. #4 slides down the shaft on #3, and sits right above the flat round part. #5 and #6 are used to retain the entire assembly, and #7 is the dust boot.

One of the grooves in the body of #4 looks like it might hold an o-ring. I'm going pop one on and see how it goes. I don't recall if it had an o-ring originally. It's also possible I got the circlip in the wrong groove, letting the piston travel too far backwards in the bore. I took everything apart to paint the M/C body, and forgot to take pictures during disassembly. That'll teach me. Anyone have this sorta master cylinder apart recently?

[Nessism]

Your order is correct. Make sure that really small hole is open and then draw a vacuum on one of the caliper nipples to suck fluid out of the reserviour and prime the cylinder. After that it should start pumping.

[Turtleface]

Your order is correct. Make sure that really small hole is open and then draw a vacuum on one of the caliper nipples to suck fluid out of the reserviour and prime the cylinder. After that it should start pumping.

What about the O-ring around #4? Am I correct in assuming it's supposed to be there? I can't recall whether it was present during dis-assembly. On #4, one end is round, and the other is square. Which end faces towards the left, in relation to my first picture?

[Nessism]

What about the O-ring around #4? Am I correct in assuming it's supposed to be there? I can't recall whether it was present during dis-assembly. On #4, one end is round, and the other is square. Which end faces towards the left, in relation to my first picture?

O-ring is suppose to be there and your orientation of #4 is correct. Basscliff has the 1980 1000 supplement manual and inside there are some good photos showing that particular style master cylinder.

[Turtleface]

O-ring is suppose to be there and your orientation of #4 is correct. Basscliff has the 1980 1000 supplement manual and inside there are some good photos showing that particular style master cylinder.

Awesome, never though about cross referencing another model, though I should have, considering how many parts swap between years. Got everything back together again, seems to be pumping fluid just find now. All for want of a simple o-ring. On to the next project!