Topic: Brakes

[Angiey2002]

Hi Guys. Moved on to the front brakes now. I have replaced all lines with new ones and when I went to fill reservoir the fluid would not go anywhere. I put an airline onto the bleed nipple hole and gently expelled some air and bubbles starting coming from the two holes in the reservoir up through the fluid I had put in it so no blockages from the reservoir to the caliper. I also gently put the airline on top of the holes in the reservoir and air came out the end of the master cylinder when the banjo fitting was off.I have been pumping the lever with the bleed screw loosened to no avail. Any suggestions?
Thanks

[Patrick]

Close the bleed screw, then pump it, then release the pressure. Repeat.

Patrick

[Angiey2002]

Hi. Ive tried that but the fluid is not moving out of the reservoir and no pressure is building up.

[KRONUS0100]

OLD TRICK....TAKE LINE OFF END OF MASTER CYLINDER....plug hole with a finger, very rapidly work brake lever....should feel pressure start to build against finger...do this until fluid wants to seep out of master on its own...hook up lines and bleed normal.  good luck.

[Bob Wessner]

OLD TRICK....TAKE LINE OFF END OF MASTER CYLINDER....plug hole with a finger, very rapidly work brake lever....should feel pressure start to build against finger...do this until fluid wants to seep out of master on its own...hook up lines and bleed normal.  good luck.

I used a variation of this after 20+ yrs sitting and completely rebuilding the system. I removed the bleed screw at the caliper and covered it with my thumb while alternately working the lever and covering/uncovering the hole. Then finished, that is fluid had filled the caliper, finished with the usual method using the bleed screw. Just keep and eye on the level of fluid in the M/C.

[Angiey2002]

I have done as you say but still nothing. There is very little pressure when I put my thumb over the end of the master cylinder. A little but nothing much.I took the lever off and used a pencil to operate the plunger in case it was not getting enough travel. This was slightly better but not enough. I was going to overhaul the cylinder sometime anyway but as I dont know much about the history of the bike, I was waiting to see what the pressure was like after I put the new brake lines on. Would the reason for no pressure with my thumb over the end indicate a master cylinder overhaul or could it be something else within the cylinder?

[754]

If you cant get pressure with your finger where the banjo goes in the end of the M/C, there is no point in trying to fill the rest of the system.

[Bob Wessner]

If you cant get pressure with your finger where the banjo goes in the end of the M/C, there is no point in trying to fill the rest of the system.

I agree. Personally, I would disassemble, clean and overhaul the entire system (it's not difficult). There's a great deal depending on it working properly every time.

[Angiey2002]

Thanks as always guys. Master cylinder rebuild it is then.

[Steve F]

If you can, get a vacuum bleeder and try sucking the fluid through the system.  I have better luck with this than with any other means.  Just keep the fluid level up to avoid sucking air.  Speed bleeders on the calipers will help too.

[Angiey2002]

Took the MC off tonight and it is absolutely caked inside with crud, rust etc. Couldnt get the circlip out so left it soaking tonight in wd40. Ordered a rebuild kit off ebay, should be here Wed/Thu.
Hopefully that will do the trick.

[Patrick]

Then we'll chat again Wednesday or Thursday when you're trying to get out the circlip from Hell....

[Steve F]

Took the MC off tonight and it is absolutely caked inside with crud, rust etc. Couldnt get the circlip out so left it soaking tonight in wd40. Ordered a rebuild kit off ebay, should be here Wed/Thu.
Hopefully that will do the trick.

Oh yuk!  Been there....done that.  I made a mistake of trying to hone out the M.C. bore to clean it up and smooth it out.  Take my advice and don't try it.  Hones were intended to be used on iron, not the die cast zinc or aluminum alloy the M.C.'s are made of.  I almost ruined it. 

[Angiey2002]

  Im going to spend the next couple of days trying to figure out how to make a tool to get the clip out. I'm eyeing up a couple of the wifes cooking skewers just now . I have seen a post in the historic section that by putting the lever bolt back in place, insert the MC in a vice lever end up, use a screwdriver and place it under the bolt and place it on top of the piston and use the bolt as a lever by pulling up on the screwdriver. It gets the piston down therefore giving you more space to work. One hand on the screwdriver and one hand prying out the clip. Another pair of hands would be handy but cant ask the wife as she would figure out what happened to her skewers

[Angiey2002]

Finally got the sucker out last night or this morning I should say.  still at it at 1 a.m. . Actually broke one of the lugs with the small hole and I thought Oh Oh what do I do now and then I noticed it had come out of it's groove enough to get a small screwdriver in behind it to bend the end up where I could get a hold of it with a pair of long nose pliers and out it popped. Probably took about an hour all told wiggling and chasing it round the groove etc. At least now I have done it and wouldnt be too phased the next time. Is it as hard to put the new one in??? The piston. seals etc were covered in crud but the cylinder looks ok so hopefully all will be well when I replace them hopefully in a couple of days time.

[Patrick]

It is a whole lot easier putting those circlips in than getting them out. Your battle is won.

[Angiey2002]

Woo Hooo as the great Mr Simpson would say.

[Patrick]

One last thing, soak the rubber parts from the rebuild kit in brake fluid before assembly. It will go together easier and also provide lubrication when you start pumping again to get fluid through the system. Get fluid to pump from the master cylinder assembly before you attach the line, and fill the brake caliper with fluid before you attach that end of the line.

[Angiey2002]

Thanks for the tip Patrick. Much appreciated.

[TwoTired]

 You are far better off using brake assembly fluid rather than brake fluid.
Glycol based fluid is hygroscopic, meaning is absorbs water, and it will do so from the humidity in the air. The rubber bits that straddle the line between containment and atmosphere, need to NOT have brake fluid exposed to atmosphere as that invites corrosion.

Assembly fluid, while acting as a lube, dissolves readily in brake fluid on the containment side, yet does not attract water on the atmospheric side.

Assembly fluid can be hard to find these days, though.  Raybestos makes a lubricant called BAF-12 Hydraulic Brake Cylinder Assembly Fluid that contains a polyalkylene oil and rust inhibitors.

Cheers,