Front master cylinder won't pump

[Grimace]

I took my m/c off, and disassembled it. Cleaned all the parts, and reassembled it using the old seals and cup. They were nice and pliable, and had no visible damage. I lubed the seals with dc4, a slick lubricant I use when assembling hydraulic components on airplanes. I put it back on the bike, filled it with new brake fluid, and it will not pump. I squeezed the lever a couple dozen times with no luck. I removed the brake line, and tried the handle again. Just a tiny dribble of fluid is all I got. Should I try rebuilding it again, with a new kit? Or should I just try to clean the dc4 off and try again? Thanks in advance.
Justin

The clymer manual is pretty vague, but I am pretty sure I got it back together correctly. I didn't have all of the parts listed in the breakdown. This is the first time it has been apart according to the previous owner.

[Do Lee]

What model is your bike 79 Standard, Special, 1.1, Sport.......

When you were trying pressure up the M/C to bleed the lines was your M/C level? If the M/C is not level you can have an air bubble in the piston chamber and you will have a hard time removing that air bubble. I always add brake fluid in the piston chamber right up to the threads to eliminate the chance of an air bubble when I rework brake systems. The Special model have this problem because of the way the M/C sets on the handlebars.

But you need to make sure that you re-assembled the brake M/C properly.

[John]

Try reverse bleeding from the caliper up to the master cylinder.

[Bud Manley]

make sure your little fluid return holes are clean. The plastic cup pops out but I had to pry it with a screwdriver. Underneath are the little holes for the fluid return. Mine were filled with pretty red crystals.

[Grimace]

The m/c is definately clean. I scraped a ton of goop out of it. The m/c is level to the world. My bike is a 79 xs1100. I used nitrogen to purge bleed holes, or splooge holes. It may be missing a part or two, but I have a new kit coming so I will post my results. Thanks for your replies.

[Pat Kelly]

Every time I've gone through the front brakes on my XS's (1100 and 750) I could not get them to pump-up. I've been an automotive front-end and brake mechanic for 25 years and have done many thousands of brake jobs.
Every time with the XS I just went riding with no front brake. After 1 or two days they pump-up as they should.
My best guess is the there is a spot where air gets trapped and road vibration gets the bubble(s) to work back to the master cylinder.

[prometheus578]

Two things to try. As Do Lee mentioned, sometimes an air bubble gets trapped at the end of the hose, or in the housing itself due to the angles involved, and which area is higher that the rest.
1: Fill the master and put the cover back on. Cut the wheel all the way to the left and squeeze the lever several times slowly. Cut to the right and do the same. Repeat till you feel foolish.
With the wheel to the left... the master is higher than the hose fitting, and any air trapped there floats into the master where the squeezing bubbles it out. Cutting then to the right moves any air that had floated past the piston next to the "splooge hole" to be expelled by squeezing the lever. Takes several(many) times to get it all out. If you're cautious, and have a spray bottle of water handy for when it squirts onto your paint job, you can do this with the cover off and watch the bubbles. When dere be no more bubbles.. you'se be done.
2: This is equally messy and will PO (Previous Owner??) your wife, when you take her turkey baster if you don't have a syringe to use. Remove most of the fluid from the master. Turn the handlebars to the left(master higher than fitting). Remove your left brake caliper and take off the pads. With a rag protecting the finish on the caliper, take a large "channel-locks" or C-clamp and push the caliper piston in all the way. This pushes brake fluid up the line and into the master, taking all air bubbles with it. Do the right caliper too, if needed.
Just 'member... compress slowly, as it will spray out the slpooge hole and hit the ceiling if done too quickly. Oh, the turkey baster/syringe is use to remove the brake fluid as the master fills up.
Still having probs? Turn the wheel to the left, squeeze the brake lever and tie it in that position using duct tape or large rubber bands. Leave over night. Bubbles will travel up and out on their own. (helps to get a wrench and starting from the calipers, lightly tap the brake hose up to the master to "shock" loose any malingering air pockets.
Large syringes can be purchased at pet stores, farm and feed joints, or from the neighborhood heroin junkie.

[prometheus578]

Reverse bleeding

Reverse bleeding, as John mentioned, is simple. Pushing in the calipers does the same thing, but the fluid supply is limited.
Go to your local cheap tool joint, like Harbour Freight, and get one o' them thar little red oil squirt cans. Fill it with brake fluid. Get a piece of clear plastic tubing (The vent hose from the battery is the right size, or use aquarium hose, but you might need to heat the end with a lighter for it to fit the caliper nipple)
Put one end of the hose on the squirt can and start a' squirtin'. Do this till all the air has been removed from the can's pump system. You now have a clear hose full of brake fluid with no air pockets.
Turn handle bars to the left again... and open one of the bleed screws on the right caliper (so you'll be close to the master to monitor it). Fluid should start to ooze out. While slowly squeezing the oilcan pump(so that the line drips) place the hose on the caliper nipple. (The idea here is to not introduce any air bubbles while hooking this up)
Now you can pump fluid up through the line... pushing any bubbles ahead of it. Again, you must have someway to remove the extra fluid from the master as it fills.

[pathfinder]

Unless I missed it

Nobody said anything about bench bleeding the M/C before you install. There is also a special banjo bolt that you can get from Dennis Kirk I've heard about it and seen it but can't find on there site right now. It has a bleeder screw on the end. You use it at the connection of the two front hoses. That connection is the air trap in the system.
Also make sure you do not pump closer than 1.5" from the grip or you will dislodge the cup on the plunger.

[Grimace]

Lot of great advice. One thing I will probably have to look into is the cup being dislodged. I pulled the lever all the way until it touched the grip. Thanks a ton guys.

[prometheus578]

dislodged plunger cap

Pathfinder,
I've 'heard" the dislodged "plunger cap' thing before. Granted, I've only worked as a motorcycle mech for four years, but have never encountered this.
No, I'm not trying to be sarcastic, just trying to get to the meat of this thing.
As I see it... The only thing that holds the cap to the plunger is the tension of the spring at the end of the chamber. As the chamber that the pluger and cap travels in is of a constant diameter, with the spring holding the cap solidly to the plunger at all times, I can see no way for it to be dislodged... there being no room for it to go anywhere else but back and forth with the plunger.
If the plunger chamber is loaded with solidified brake fluid and other gunk, as I have run into, it may hang up and stick, but with the spring holding it solid to the end of the plunger, it can go nowhere.
Now I have run into instances where there is so much gunk in the passage that the pluger sticks to the point that the spring can't push it back to it's starting position. I have then pulled on the plunger... freed it... and then found that it slides back and forth freely... having become separated from the stuck cap and spring. This is obviously an extreme condition, and not something encountered during routine bleeding or maintenance of a fairly clean master cylinder.
Can you explain more about how the cap can be dislodged for me, or just provide your thoughts, in general?
Again, not trying to be a jerk... just looking for new info on the "how comes..." and "why for's..." of brake systems.

[rickmcdougald]

My XJ11 brakes ...

Grimace,
Good luck on your XJ11 brakes. I've gotten seal replacement kits for both M/Cs and all three wheel cylinders. They were all full of "jelly" when I got Arlington. I don't think that they'd received any attention in the previous 22 years before I'd gotten her!

I bench bleed my M/Cs 'cause it's a good start.
(I've had to "stand on my head" to perform brake jobs on some small aircraft.) Doing it on the motorcycle is a breeze!

If you decide to replace the wheel cylinder seals, blow out the piston with the master. If they've already been disconnected, use a grease gun on the bleeder zerk to blow 'em out.

From my aviation experiences, I've still got a large tube of Dow Corning #4 from the '80s. It has no equal!
The same goes with Parker O-ring lube (aka monkey sh*@) and Fuellube - gasoline-resistant grease.

RLMcD A&P

"Just remember, there's always someone who's got it worse than you!"
-My Dad

[Grimace]

I have a big tube of dc 4 and a can of fuel lube. I used the fuel lube on the oring for the master cylinder, but I think the dc4 might be too slick to allow the m/c to prime. I have started taking it all back apart, and am waiting for my rebuild kits to come in. As soon as they do, I will rig up a pressure bleeder for the entire system, and back bleed it from each caliper. I have done that on LBF planes before, and it seemed to work great. Thanks again for all the help, I knew this site would be a good one.

Justin Padgett A&P