Triumphrat

Klicker · 06-04-2005

I have just rebuilt the rear master cylinder and caliber on my 76 Bonnie. After bleeding the brakes They hold for a while then fade. But it is not losing any fluid that I can find. Rod :???:

KuzzinKenny · 06-04-2005

There must be air in the system, try bleeding it again and see if this helps.

KK

Klicker · 06-04-2005

I have blead them three times. The last time it held for a day. Rod :???: :???:

jimballard · 06-04-2005

From my auto repair days: Recheck the master that you rebuilt as there may be an "internal bypass" situation happening. The fluid may be going past the piston under pressure, but, of course, it never leaves the unit. If so, you'll have to do it over; also, if this is the case, check for any corrosion or scratches on the cylinder bore.

Just my $.02 worth: Jim

Lutz · 06-04-2005

Hey Klicker,
When you bleed the rear brake the caliper must be hanging down with the bleeder to the top of the caliper.
If not done this way all of the air cannot be removed.

Lutz

OzBloke · 06-05-2005

Klicker,
Easiest way to do this:
Bike on centre stand, take out bottom shock asborber bolts. Loosen top bolts, and swing shocks backwards and up away from swing arm. Put a block or brick under rear tyre to bring rear axle bolt above mufflers. Take the torque link bolt off where it attaches to the swing arm. Take axle nut off, and with dowl or big bolt, tap out the axle until it just clears the plate holding the caliper in place. Swing the caliper off the disk, and put two wedges of wood or screwdrivers in to keep the pads apart. Using wire, hang the caliper off the swing arm (so as not to have all the weight on the rubber hose). With Bleed nipple at the top, bleed the system again, remembering to constantly check the level in the reservoir under the seat. Then put it all back together.

Good luck with it.

[ This message was edited by: OzBloke on 2005-06-05 18:00 ]

Lutz · 06-06-2005

Klicker,
The easier way is just pull axel enough to let caliper t swing down and hang on strut use screwdriver approx. 1/4" thick as a spacer bleed brake ane re assemble.

Also when rebuilding Cylinder or caliper be sure to remove resevoir from its mount and make very sure that the small holes in mount are open.If they are plugged the fluid cannot return causing brake to drag also difficulty in beeding.

Lutz

papereng · 06-08-2005

Could be the re-assembly of the master cylinder wasn't done correctly. It is very important to get the piston positioned in the bore so as to allow the correct stroke fully across the fluid supply passage. It must open the supply port when retracted to allow fluid to move in and out of the cylinder, but must also close it off completely when applying the brake. (The Triumph manual will tell you the the rear cylinder can't be rebuilt, and to replace it - this is not true, but this issue is why they don't want the owner rebuilding the rear cylinder). The Lockheed manual gives the following procedure for the rebuild and reassembly of the rear cylinder. Assuming the cups are correctly installed on the piston and the spring and piston assy are installed in the bore, reassemble the cap by screwing it on until first contact just occurs with the plunger flange. Make a reference line on the barrel and the cap at this point with a marker. Next screw the cap onto the barrel (1) full turn until the mark lines back up. Now continue to turn the cap onto the barrel until the locking set screw lines up on the key / groove. This will be less than a full turn (in no case go more than 1+ a partial turn total). Lock the cap set screw in this position. Now set the stop screw clearance for the plunger travel to the spec. in the service manual (I think it's .374" / .376", but check this - if you need the exact number, I'll look it up for you). This procedure positions the piston correctly in the bore relative to the fluid supply passage. The piston must completely pass the supply passage to prevent hydraulic leak-back to the reservoir when applying the brake.

Try this out and see if your problem goes away. Good Luck.

[ This message was edited by: papereng on 2005-06-08 10:28 ]

Klicker · 06-09-2005

I want to thank everyone for there help. I dropped the caliper down and put in a piece of flat steel for a spacer and this worked fine. I had the master cylinder off and apart twice and a friend did it once to check that I had not screwed it up he is a mechanic so he knows more then me. In one of my books it says about having to drop the caliper to bleed it. I had read it before but forgot. Rod