82 450L master cylinder question...

[Ishamael]

OK, 2 questions:

First:

Inside the master cylinder, there are 2 small holes in the bottom.

The one towards the back (closest to the handle plunger) goes all the way down, and you can watch the plunger move in and out.

The front one (closest to the brake hose) seems to have a pinhole in the bottom. What is the function of this hole?

I ask because it was clogged with junk and I am cleaning it out, and wondering if I need to really get into that pinhole and clean it out somehow.


Second:

If I fill the master cylinder with fluid and attach the cap, disconnect the brake hose from the front, and squeeze the handle, no fluid comes out.

I take it this should not be happening, right?

Thanks!

[Nessism]

I believe one hole feeds fluid into the piston, to be pumped down to the caliper, and the other is a return so to speak - sends up a stream of fluid when you squeeze the lever. Both need to be clean - you know this of course.

The reason your master is not pumping is because you have air in there and need to prime the system first. Check the following thread for more info. http://www.thegsresources.com/_forum...ad.php?t=98788

Good luck.

[Ishamael]

Thanks, Nessism.

You'll have to bear with me, I've never done brakes before. I don't know how, but I've never really had to do anything but change pads and rotors.

So I've got the Master Cylinder off the bike, and the handle disconnected.

The reservoir is full and the top is off.

I push the piston all the way in with a screwdriver, and a bubble comes up. (so far, so good)

Then....the piston never pops back out again. What am I doing wrong?

[Nessism]

Thanks, Nessism.

You'll have to bear with me, I've never done brakes before. I don't know how, but I've never really had to do anything but change pads and rotors.

So I've got the Master Cylinder off the bike, and the handle disconnected.

The reservoir is full and the top is off.

I push the piston all the way in with a screwdriver, and a bubble comes up. (so far, so good)

Then....the piston never pops back out again. What am I doing wrong?

You are not doing anything wrong. BUT...your master needs to be rebuilt. The piston should return by itself - there is a spring in there pushing it back.

Pull off the rubber boot and have a look down the bore at the C-clip. Next, find/borrow/steal the proper circlip pliers so you can get down there to get that bastard out of there. Cuss words are appropriate for this job so make sure you have lots of beer, or equivalent, before you have at it. Key thing here is to have the proper tool. Don't ask me how I know.

[Ishamael]

Yeah, I can see the spring in there if I look down the end where the banjo bolt goes...

Hmmmm....well this isn't good, I need the bike tomorrow to drive to work.

I'm gonna keep fiddling and let you know what I find. Thanks!

[Ishamael]

OK, so sometimes the piston pops out after a while, and sometimes it doesn't.

But I can't see anyway to get that boot off the end of the piston without ripping it to shreds. Ideas?

[Nessism]

The boot just pushes into place. Maybe it's stuck due to corrosion?

[Ishamael]

The boot just pushes into place. Maybe it's stuck due to corrosion?

Oh, you mean pull the spring out the end where the banjo bolt goes! Will I ever be able to get it back in??

[Nessism]

Oh, you mean pull the spring out the end where the banjo bolt goes! Will I ever be able to get it back in??

You need to pull off the small boot around the plunger where the lever pushes. After you get that rubber cover off you can see the circlip - you need to depress the plunger to get the clip out.