Piston assembly rear break removal

[flyin900]

[flyin900]

My head exploded when I read this.

I’ve had a rebuilt rear brake caliper lock up twice and couldn’t understand why. When I rebuilt the master I saw the indentation in the reservoir that I thought had no hole in it and re-assembled without clearing it. I didn’t know it was actually there. You just saved me a world of work as I’m now rebuilding an entire rear system on a second GL1100. You guys are lifesavers.

We've all likely been there at some point with brakes, unless we read a forum members experience with the pressure return hole. The FSM doesn't really cover it well, or the consequences of it not being clear.

[Prospect]

Update. I took the rear brake master cylinder apart and managed to get the reservoir off as well. Cleaned the splooge hole and put in new check valve, spring, piston, circlip, push short, boot. Installed it and tested it out after bleeding. It sort of works. The caliper piston moves but doesn't retract. I have to hit it with a mallet to relaese. I'll have to install new piston seals and try again.

[flyin900]

How clean is the seal groove inside the caliper? It needs to be really clean of any old dried brake fluid, or it can cause the seal to bind on the piston. If it is really clean then I would look at your brake line as a possible culprit, as they are known to sometimes collapse internally from age. John Demara knows about old brake lines and internal collapse.

Sirus Consolidated has a OEM style rear replacement brake line for you bike at a reasonable cost.

[taunusrainer]

generally I doubt that PB Blaster is a good choice for brakes. It s mineral oil based afaik. Causing rubber parts to swell and that will not help to get parts apart.

[Prospect]

I took the rear brake apart to do a proper job. I got the piston out by using heat and compressed air. It looked as expected and I should have done it the first time I had the caliper off. Cleaned everything up and I'll reuse the seals unless I can get them quickly. I have to order new pads anyway.

[Prospect]

How clean is the seal groove inside the caliper? It needs to be really clean of any old dried brake fluid, or it can cause the seal to bind on the piston. If it is really clean then I would look at your brake line as a possible culprit, as they are known to sometimes collapse internally from age. John Demara knows about old brake lines and internal collapse.

Sirus Consolidated has a OEM style rear replacement brake line for you bike at a reasonable cost.

Thanks for the tip! I'll contact Sirius.

[flyin900]

There was a lot of crud in there, so if the seal groove is really clean then hopefully you have solved your brake drag issue. When your servicing one area of the brake system it is prudent to do it all, as your going to have to bleed the system anyway.

[Pb9717]

This is a picture of the area of the rear master where the reservoir hose connects to the body of the master. On the bottom there is a hole that feeds the cylinder and an indentation that appears to have no exit, or is plugged. Is this the passage that permits the caliper to retract? And If so , it appears thoroughly clogged. How do I clear it? Can it be drilled? A guitar string is having no effect.

4EA3F94C-993A-45B6-ACAF-C63E638E80C2.jpeg

[flyin900]

Yes that is the hole and no do not drill it and risk enlarging the hole. Unless you have one of those really tiny pin drill kits and the extremely tiny drill bits that come in that set. The key is not to enlarge the hole beyond the original opening size. I have used a single strand of wire plucked from a wire brush in the past, yet again care is needed not to enlarge the tiny hole. If you can boil the entire assembly while it is apart, it may help in dissolving the crud in there.
Brake cleaner and compressed air if boiling isn't an option, or others may have some tips and tricks that worked for them

[Pb9717]

I was able to clear the hole with a high E guitar string. It is an extremely small hole in that a B String would not clear the diameter. The hole must be less than 12 hundredths of an inch. Good news is I was able to clear it. Master is now reassembled and hope everything will operate as designed. Thank you for the assistance.

[pidjones]

I was able to clear the hole with a high E guitar string. It is an extremely small hole in that a B String would not clear the diameter. The hole must be less than 12 hundredths of an inch. Good news is I was able to clear it. Master is now reassembled and hope everything will operate as designed. Thank you for the assistance.

There you go! Now, save that string for pilot jets!