Washer under circlip front master cylinder

[jknappsax]

After I had used the front MC to pop out the piston in the front caliper of my 1979 GS 1000 to rebuild it, the mc wouldn't build up pressure. I bought a piston cup/spring rebuild kit. When I pulled the mc apart, I swore that there was a washer with a circlip above it that held the piston cup in place. When I opened the parts, there was everything but the washer. I honed out the bore to get rid of some corrosion and a scratch, and in looking at the bore for a seat for the washer, there didn't seem to be one. There was a groove for the circlip, but other than that, the bore size was consistent. I put the mc back together with the circlip holding everything in place. The mc did not develop pressure. Was there a washer under the circlip, or did I misremember the assembly? I can't find a fiche that shows anything clearly enough to see a washer. I have another mc from a GSXR 1100 that I'll put on in it's place, but the original not working after a rebuild is really bugging me. Any suggestions as to where I went wrong?

[Rover]

This is what came out of my GS1000,14mm MC
I believe the 5/8 is similar except bigger diameter.
No washer.

[Hornswaggle]

I know it could be different from my 450 but I just rebuilt the mc and the parts look just like Rover's picture. Mine did have a washer under the circlip and there was a new washer in the rebuilt kit.

[Souske]

Just got done rebuilding the master and calipers on my 80, likewise no washer. Did you bleed the system? If there are air bubbles, the system won't build pressure

[jknappsax]

No washer

My mc is exactly like yours, Rover. It seems that putting a washer on the plunger would cause it to bind in the bore if it cocked, as there would be no shoulder for it to rest on. Souske, I've done several complete brake rebuilds, and understand the bleeding process. It was while I was bleeding the system that I became aware of the lever never firming up. Never had this type of trouble before. I bought a 14mm Flexhone to resurface the bore, maybe I was a little too aggressive in my honing, as there were a few corrosion spots, and a longitudinal scratch in the bore. But it does make a weird noise while pulling in on the brake lever, almost like it is sucking air in somewhere.

[2BRacing]

Just for comparison, the specs on a 850 master cylinder are 15.87 mm bore diameter and 15.80 piston diameter. You should measure yours to see if the clearance is not too large due to maybe honing too much.

[Souske]

OP: I didn't mean to be condecending, there are people of all skill levels here, I was just hoping it was something simple. Good luck in finding your problem

[jknappsax]

No offense taken. Any suggestions gladly accepted. 2B, I agree. As someone here has as their sig line: "To measure is to know."

[LarryC]

I had the same problem- difficulty getting any kind of pressure in the system. The answer I found is suction. And your lips are not strong enough. I dug around the garage and found a weedeater spray device which sucks the liquid into the handle where it is under the pressure of the return spring to spray. Well, it sucked the brake fluid just fine! And the hose fit the bleeder too! I hear there is a device for sale which will accomplish this. I now have great pressure- too much almost! My brake handle moves about 1" before the brake bites.

[chuck hahn]

That device is called a Mighty Vac.

[Souske]

I use this: http://www.harborfreight.com/brake-f...der-92924.html

[chuck hahn]

The mighty vac on the right side of the page is what I have..I like the Pneumatic one though.. I work right over by a Harbor Freight. Will have to stop in one day on the way in.