1982 GS1100 Front Brakes arent making pressure

[Gorminrider]

I'm starting to wonder if the T joint is cracked where the banjo bolts thread in?....or something is stopping the banjo end and washers from mating to flat surfaces? because It's not my experience that the banjo bolts or washers in themselves are at all difficult to seal.

It's more difficult with twin discs but you might have better accessibility if you remove the t joint from it's mount and even replumb the system so it's out where you can see all round it properly.

You can even remove the entire system to the bench, putting clean thickness of wood in to replace the discs...

[dorkburger]

Regarding the master cylinder. I usually get the noted tiny bubbles from the hole. When this happens I slowly work the lever in and out, but only go about 1/2 - 3/4 of the way in. I keep the cap off to observe and go slow to prevent the "fountain". There is often a surprising amount of tiny bubbles released.

[FlordiaMan]

I'm starting to wonder if the T joint is cracked where the banjo bolts thread in?....or something is stopping the banjo end and washers from mating to flat surfaces? because It's not my experience that the banjo bolts or washers in themselves are at all difficult to seal.

It's more difficult with twin discs but you might have better accessibility if you remove the t joint from it's mount and even replumb the system so it's out where you can see all round it properly.

You can even remove the entire system to the bench, putting clean thickness of wood in to replace the discs...

Im not sure but when i took the crush washers off, they were pretty crushed. I could clearly see where they sealed. Im thinking there is something in the connector thats not allowing it to build pressure. There was a decent amount of rust in the old lines and i wanna say some pretty good rust in the T as well, so the threads might have become too worn to properly seal. Thats just my guess however.

[Gorminrider]

The old washers must have been squeezed on pretty tight. Hope the threads arent stripped...They needn't be flattened to seal. Just tight (if you are prone to yarding on bolts, try a torque wrench if you have it ...)
If the threads were leaking, the washers should stop any leaks anyways if the surface of the T is flat and reasonably smooth. If the banjos tighten ok it shouldn't leak.

On some bikes, the T has an indentation to limit the angle of a brakeline attached to it. That'd be worth a look just to see if the metal end of the brakeline isn't hanging up on a ridge that controls that angle or even on backwards with the angled end hung up stopping a seal ... On my bikes with dualcalipers, I cant see much for cables, forks,wiring...that's why I suggested getting the T out where you can see it closely.

[FlordiaMan]

Guys, i am really starting to get fed up. There is NO logical reason that these brakes shouldnt be building pressure. Both calipers will pressure, both master cylinders work, put it all together, IT WONT WORK. I tried a new tee, still nothing. I reversed bled, i took the whole thing off the bike and held the calipers over the M/C, STILL NOTHING. This bike just doesnt want to stop! I dont even know if any of the shops around me would be willing to even look at them because they are too old.

[Nessism]

What brand caliper pistons and seals?

[FlordiaMan]

Stock calipers and OEM seals

[Nessism]

New OEM seals? Stock pistons?

[FlordiaMan]

New OEM seals? Stock pistons?

No its OEM pistons too, its the seals that came with the OEM pistons.

https://www.onlinecycleparts.com/oemparts/a/suz/50d40449f8700230d8b4ed1e/front-calipers

These are the pistons i bought, they came with new OEM seals.

[Nessism]

What size piston on your new master?

It sounds like the pistons are not moving out close enough to the disc. This happens when the pistons are binding. Tying back the lever after pumping it up usually helps although it seems you tried that already.

[FlordiaMan]

What size piston on your new master?

It sounds like the pistons are not moving out close enough to the disc. This happens when the pistons are binding. Tying back the lever after pumping it up usually helps although it seems you tried that already.

Im not sure, it was the pistons i ordered off cycle parts for my bike. However my pistons are closing just fine, and i can even press on the bike and the front tire wont move, its just that i can pull my handle all the way to the grip.

[Nessism]

If your master has a 14mm piston it will never have a firm lever feel. You need 5/8" or 16mm.

And it's not a matter of "pistons are closing just fine." The pistons move out of the caliper bore and close to the disc after the rebuild then when you press the lever they just move ever so slightly to make solid contact with the disc. It sounds like yours aren't moving close enough.

[FlordiaMan]

If your master has a 14mm piston it will never have a firm lever feel. You need 5/8" or 16mm.

And it's not a matter of "pistons are closing just fine." The pistons move out of the caliper bore and close to the disc after the rebuild then when you press the lever they just move ever so slightly to make solid contact with the disc. It sounds like yours aren't moving close enough.

Wait... is that not normal! Like when i press my pistons in they push, but when i release they move back. Thats not normal?!?!

[Nessism]

During a caliper rebuild the piston is pushed deep into the caliper housing.

The first few times you pump the lever the piston walks out of the caliper and moves closer and closer to the disc. When in the proper position the piston (as spaced by the pads) are just a few thousands of an inch from the disc. Then when you pump the master pressure builds and the piston moves closer still, only it doesn't actually slide in the seal, the seal sort of flexes towards the disc when pressure is present. When you have binding in the caliper the piston doesn't move close enough to the disc so you get a firm lever. You grab a handful of lever and the piston moves towards the disc but doesn't make full contact before the lever travel is gone. You need the move the piston closer to the disc, then when you pump fluid from the master the pads will make strong contact and you will get a firm lever.

[FlordiaMan]

How do i get the piston closer to the disc?