Front brake pad replacements

[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.

 

[Alexander]

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.

yes the calipers have been overhauled, but I remember sanding the pistons, with little success, due to some stains with loss of material, probably being stationary for a long time,
during the rest phase the pistons lost the necessary shine for the seal, even the seat of the gasket on the alloy of the caliper was not perfect. The unobtainable OEM pistons
will be replaced and if they are not these but the ruined alloy, both on the calipers and in the pump seal, I have no choice but to replace the system.
I will do a search to see which other bike, perhaps more recent, had the same calipers, maybe the ones from the 850.

 

[salty_monk]

What year is your 1000G? If it's 1980+ then you can use anything from any of the 82/83 Twin brake bikes. Personally I moved to the twinpot partly for that reason, good stuff is getting rare now...

 

[Alexander]

I replaced the bleed screws, but I didn't see any improvement.
It brakes perfectly, but the brake lever sometimes feels loose.
I think it's due to the seal, and given the rust on the cylinders, I think it could be their fault.
Thanks for the tips!

 

[salty_monk]

You can upgrade to the twinpots on that bike. That would be my next move if you think the pistons are shot.

 

[lizzywhite45]

Try switching to organic pads, as ceramic ones often need heat to work properly. Also check for any air in the system. This guide on brake pad types explains what works best and why.

Test

 

[Grimly]

https://www.vikingbags.com/blogs/news/all-SPAMMING-CRAP?

Right you are, spammer.

 

[Alexander]

You can upgrade to the twinpots on that bike. That would be my next move if you think the pistons are shot.

You're right, that will be the next move. Best!

 

[salty_monk]

You're right, that will be the next move. Best!

In case you need a link to the mega thread.... https://www.thegsresources.com/_for...nk?140253-Twinpot-Brake-upgrade-on-78-Skunk/=