Topic: Brake Caliper O Rings

[MauiK3]

1973 CB 750 K3, dual discs, stock master cylinder, stainless lines, new caliper pipes.
I've been having trouble with the right caliper hanging up and not retracting which drags and squeals. I've taken it apart and can find nothing hanging up or any metal to metal problems. The caliper assemblies are new, no corrosion.
I'm thinking the rubber o ring is somehow defective and I'm looking to replace it.

My question is, looking at David Silver, I can get an original part or an aftermarket. I normally would go original but I wanted to see if anyone had any information on the performance of aftermarket o rings vs. Honda, are the rubber compounds similar, do they perform the same?

Does one retract the piston better than the other?

I'm not really concerned with the cost difference, it's brakes!
Maybe I'll get both to do a comparison, if I need to.

[bryanj]

Do you mean the piston seal or another O ring

[RAFster122s]

If the hose isn't collapsing inside, then the master cylinder has a tiny hole that can get blocked not allowing the fluid to return causing a caliper to hang up. See if you can clear this hole with a very fine wire.
But, your having new stainless brake hoses would negate the hose collapsing causing the problem. If it is only on one side then it isn't the master cylinder problem.
Aftermarket and stock seals are essentially the same... It is a square section seal. The groove for the seal has to be spotless. Check with a dental mirror. If it is spotlessly clean then fit a new seal.

[BenelliSEI]

+1 to what RAF says. I have a small, flat blade screw driver that I’ve bent the small tip 90 degrees and keep sharp. I use it as a scrapper for the seal grove. After that, I fit a small, brass wire wheel to my Dremel and polish the groove until spotless. Any “lumps” in there cause piston drag. If your original seal is not leaking or damaged, just try this and put it back in........ Good Luck.

P.S. make sure the caliper pivot is free and well lubricated as well.

[MauiK3]

Thank you, I’m hoping to get this fixed.
I’ll get
A new piston and a few seals and see what happens.

[bryanj]

Dont know about your side of the pond but there is a seller on UK ebay that does stainless pistons with seal for a good price