Front brake pad replacements

[Alexander]

Dismantled the whole system, cleaned the pump again, it is not in good condition, but it seems impossible to find, perhaps the one from the 550 could be adapted. Seals and spring already replaced a few months ago. The oil has small black streaks, certainly material that comes from the original pipes, I should replace them even if externally they do not show cracks or particular signs.
I have not dismantled the already overhauled calipers. Oil and several bleeds but unfortunately the lever continues to have too much movement almost at the end of run.
The first pumping is the worst, then it improves slightly. In the end I adopted a homemade solution, with a simple 1mm washer I recovered a lot on the lever and now it has improved considerably. Sooner or later I should replace everything, but I do not want to change the system model.

[gustovh]

Bleed your breaks, you have air in the lines.

V

[Alexander]

Bleed your breaks, you have air in the lines.

V

Hi, I've bled at least 10 times and the last 5 without seeing a small bubble. Maybe it stops in other areas and not on the calipers?
I think it doesn't stay under pressure and it takes air from somewhere. It's just the first pump that the lever goes down too much, then it gets better

[Grimly]

Euro-market GS1000G with the 1980-onwards calipers?
Don't make the mistake of using too small a master cylinder with them, it will work great on the second pump, but there's too much lost motion with these calipers to make them safe with a small master cylinder.
Use a 5/8" bore m.c. with adjustable lever span. I use Honda Deauville m/cs on mine and they match the calipers fine, with Carbon Lorraine pads that are excellent.

[Alexander]

Euro-market GS1000G with the 1980-onwards calipers?
Don't make the mistake of using too small a master cylinder with them, it will work great on the second pump, but there's too much lost motion with these calipers to make them safe with a small master cylinder.
Use a 5/8" bore m.c. with adjustable lever span. I use Honda Deauville m/cs on mine and they match the calipers fine, with Carbon Lorraine pads that are excellent.

thanks for the advice, it should be this one, but I see the lateral tube attachment instead of the front one and I need to understand if the tube arrives without impediments,
another thing to check is the stop switch.

[salty_monk]

You should check the bleeders. I have seen where the air bleeders will allow air back into the caliper & cause a situation like you describe. It was undetectable by eye, smell, feel etc. No fluid coming out.
One of the members on here (TomMLC) and myself chased that one for ages when he did a Twinpot brake upgrade.
He serviced & painted the calipers & replaced the bleed nipples with new shiny ones..... You can try putting some PTFE tape around the threads & bleeding again. Tom eventually went back to the old original ones once we proved the problem.

[Alexander]

You should check the bleeders. I have seen where the air bleeders will allow air back into the caliper & cause a situation like you describe. It was undetectable by eye, smell, feel etc. No fluid coming out.
One of the members on here (TomMLC) and myself chased that one for ages when he did a Twinpot brake upgrade.
He serviced & painted the calipers & replaced the bleed nipples with new shiny ones..... You can try putting some PTFE tape around the threads & bleeding again. Tom eventually went back to the old original ones once we proved the problem.

wow thanks!
it would be a turning point, because anyway with the thickness, the first pumping is slow. I will try as you suggest with a bit of teflon in the thread.
I also noticed the liquid container more swollen, not exactly perfectly aligned with the lid and its seat.
I don't know if it could have an effect.

[salty_monk]

It's something easy to try at least! Good luck!

I doubt the reservoir (container) could have anything to do with this as all the "action" is happening below the bottom of the reservoir. Even if it was leaking air at that point it would presumably just come to the surface in the reservoir and would not get into the brake lines..

As a final step to your bleeding... pull the lever back hard "on" and put a cable tie to hold it and leave overnight, sometimes that can make a real difference.

Also make sure you try bleeding the master cylinder.
Sometimes you have to wrap a rag around the brake union and with the lever removed use a screwdriver to push the piston all the way in whilst you crack the union (and then close before you let it go). There could be air getting stuck there.

[Alexander]

I ordered the bleed valves, yesterday I take a ride after checking everything and the situation does not change, the first pump does not go up to pressure, then it goes great as it should, it is as if at rest it loses the vacuum. Things could be different, or it takes air from some gasket, possible because the alloy of the calipers and the pump are not perfect, it could be the pistons of the calipers with the ruined surface, or air that cannot escape.
Off topic:
I had bought a new non-original cable for the rev counter, from about 4000 rpm onwards it started with a deafening noise, I thought the rev counter was broken.
I change the cable with an original one and everything is back to normal

[Grimly]

I'm inclined to believe it's lost motion in those calipers, if they're original and need a rebuild.
If they're too old and worn, there's nothing to be done, just replace them.