Broken brake master cylinder

[Papakeith]

I knew that I should have left it alone.:( I went out to the shed with the intention of putting on my new foot pegs and calling it a night.

But NOOOO! I decided that tonight would be a great night to replace the fluid in the front brakes.:mad: Please bear in mind that the brakes have worked fine for the last year and a couple of months without my intervention.
I had been wanting to change the fluid for awhile now. Well, last week I finally got the two screws on the master cylinder loose(without ruining them:))
That's about where my luck changes for the worse. When I started I had working front brakes.
Now, I got nuthin'.

Let me describe what I see and you guys/gals can shoot me some suggestions.

I don't know what type of fluid was in the brake system when I started. All I know was that it was brown. The bike calls for DOT 3 or 4(what's the difference in these anyway?) I used DOT 3.
When I pull in the brake lever(with the resevior full) and open the bleader, I get nothing but fluid. For the first few pumps I could see the fluid advancing down the blead tube. So far so good. Or so it seems.
It was about then that I lost all feel in the brake lever.

I notice that there is a small air bubble in the resevior. A couple of taps on the side of the master cylinder takes care of that. More show up. The fluid level never drops either.
How in gods name can there be enough of a seal for the piston to work one minute, and the next nothing at all.
Are there any other parts to the brake cylinder that I can check? All I see is two rubber seals on a shaft and a spring. Are there any other components in the housing that can be checked?

Help.

 

[Old CR goat]

were you pumping and leaving the bleed open? if so you can pull air back in from the bottom

Oh, and why is it so hard for us Old farts(I said us) to learn "if it ain't broke, don't fix it":p

 

[thorman75]

ive seen this before,doug goins the manager at service honda had the same problem on his cr250 a couple of years ago.we ended up reverse bleeding.its a syringe deal you fill with dot 5,attach to the bleeding nipple on the brake caliper,and push the fluid back up and thru the master cylinder.worked great.theyve got a power bleeder now.

 

[Papakeith]

were you pumping and leaving the bleed open?

Nope, I used the same method I've used on every hydraulic brake I've ever bled.'pump,hold,bleed,tighted, release'. I also connect a clear line to the bleeder that is terminated in a bottle of fresh fluid.
As for the second statement. . . :think I've got the tinkerers gene I guess:ugg:. The whole time, I was saying, "It works, don't "F" with it. Go inside and watch a movie".

 

[Papakeith]

Closest I can come to a syringe is a turkey baster:confused: . Can't hurt, might help.
Thanks

Wait, I've got a couple of small syringes hanging around after all! (inkjet refill kit). I might have to give this a try.

 

[Old CR goat]

Hmmm, been thinking about doing the same to mine, working fine but there's that tinker gene you were talking about.
Maybe I'll just leave it alone for a while so I don't have to come back in here and and ask you how the turkey baster worked,;)

 

[thorman75]

i dont think youll get enough pressure with a turkey baster.but your on the right idea.go to walmart,k mart,gander mountain,etc.in the sporting goods section and buy a syringe that they sell for injecting turkeys with marinade before frying them.there big enough to use.

 

[Papakeith]

I was only kidding about the turkey baster:) .
The syringe from the injet refill kit worked perfectly. Only problem is the master cylinder didn't.
I donated a new master cylinder to the 84 from the 87 CR and voila, I got brakes!:).
Looks like something(debris, muck, ect.) must have gotten dislodged that was allowing the old cylinder to work.
Doesn't say much for cleaning stuff does it?:silly:
Anyway, I'm off to see if I can replace the piston cones, or purchase some form of rebuild kit.
Thank god I don't have to bleed the back brakes on this one.

 

[whyzee]

When I swapped out for stainless steel brake lines on my Harley, I installed Russell "speed bleeders", easiest bleed-out I had ever done. I'm sure they are available in a thread fitment for most dirt bikes. If I get the need to mess with the brakes, I'll get them for the yz too.