caliper problem

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Onder said:
Is not "horse" street talk for heroin? :-(
Click to expand...

No idea what's the street lingo, I was referring to that animal that has four legs that riders can't steer and craps grade one rose manure, hope this is as clear as mud!:)
 
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Some years ago I had a problem with a Yam XS750 that came to a halt on a test ride unexpectedly. I found that I could get mobile by slackening off the brake lever adjustment screw. Then when I got home I found that the master cylinder circlip wasn’t fully seated and the piston was trying to come out. A tap with a screwdriver to seat the circlip and all was well again.
 
Mine is the opposite problem. The piston retracts too much and doesnt want to grip the disc. If you tie up the master over night it will be rock hard in the morning. It will work fine but after a few miles it just retracts and doesnt stay up in contact with the disc.
 
Onder said:
Mine is the opposite problem. The piston retracts too much and doesnt want to grip the disc. If you tie up the master over night it will be rock hard in the morning. It will work fine but after a few miles it just retracts and doesnt stay up in contact with the disc.
Click to expand...
What setup do you have Onder?

Cheers,

cliffa.
 
Onder said:
AP rear brake both master and caliper, 1971 Rickman Enfield. https://raresportbikesforsale.com/w...rickman-triumph-cr-left-rear-wheel-detail.jpg

You can see that the high point is in the hose and the angle of the master is just the worst. Down at the caliper you
have a bleeder on one side and the brake line on the other. The problem is on the line side,no bleeder there.
The line is half way up the side not at the top.
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Hi Onder, I know it's not a Norton, but the mechanicals are similar, so if you can get a hard pedal, and you're not seeing any leaks with it tied hard on, then surely has to be one of the following:

The pads are being knocked back, so check disc runout and wheel bearings. Or alternatively the system still has air in it. I've had a look at some images of the Rickman, and as you say it's a bit of a torturous route from the M/cyl to the caliper. Could you remove the caliper (still connected) place it up on the seat with the bleed nipple at the top and something between the pads and try bleeding it there? Or if not perhaps use a large syringe full of fluid connected to the bleed nipple to push fluid (and air) out ?

Cheers,

cliffa.
 
Ive tried everything and Im sure it is air. Runout is nominal. The only way to get the caliper above the master is to
take apart the body work on the bike and remove and replace the brake system intact. I should have done this when
I had the bike apart. Lesson learned. It sorely needs a bleeder on each side. The none bleeder side no doubt lets the
air somewhere.
 
RoadScholar said:
As you have read in this thread, if the inner piston is installed too deep it will either preclude bleeding or make it quite frustrating at the least.

You say that the inner piston moves with compressed air; that would indicate that the inner piston is, now, not too deep, good move. The next issue is that the "chamber" behind the inner piston has only one passage for brake fluid to enter, a "dead end" unlike the outer piston/chamber that has a feed and a bleeder; the inner would love a bleeder valve.

Pressure bleeding with any method forces the brake fluid toward the inner chamber, but leaves no way for the air to escape, sort of a one-way street. Cutting to the chase: I use a small syringe and fill the caliper slowly, I use the bleeder valve bore because it is the highest point. Drop by drop, slowly until fluid no longer enters the caliper body, and when you think you have reached this zenith step away and do something else for an hour (YMMV). If you have become so fixated that you can't leave then invite your drinking buddies or your love interest; time always passes quickly in either case.

Once the caliper is really full bleed the line from the master very gently making sure that the reservoir is the highest point. At this point you may be done, if you get a spongy feel let it have the night off, both of you will be good the next morning.

Best.
Click to expand...
Tried this today RoadScholar and it worked like a charm. I unbolted the caliper leaving it connected and moved the inner caliper out by pumping the brake a little, then injected new fluid into the bleed nipple. It took a fair amount before raising the level in the master cylinder reservoir, indicating that there was air behind the inner piston. Now the lever action is superb. I had tried lever bleeding, vacuum bleeding, injecting from the bottom, securing the brake lever overnight. Nothing had worked. Thanks much.
 
Onder said:
Ive tried everything and Im sure it is air. Runout is nominal. The only way to get the caliper above the master is to
take apart the body work on the bike and remove and replace the brake system intact. I should have done this when
I had the bike apart. Lesson learned. It sorely needs a bleeder on each side. The none bleeder side no doubt lets the
air somewhere.
Click to expand...
I would definitely agree on there still being air in the system, try reverse bleeding through the calliper bleed nipples using a syringe
My Magura master ans AP calliper took several attempts to bleed.... but a 60ml syringe bleeding both ways through the bleed nipple did the trick
 
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