Piston assembly rear break removal

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flyin900
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Re: Piston assembly rear break removal

#16

Post by flyin900 »

action1
Last edited by flyin900 on Thu Nov 25, 2021 9:40 pm, edited 1 time in total.
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
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flyin900
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Re: Piston assembly rear break removal

#17

Post by flyin900 »

flyin900 wrote: Thu Nov 25, 2021 9:36 pm 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. type1
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
Prospect
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Posts: 40
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Location: Toronto Canada

Re: Piston assembly rear break removal

#18

Post by 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.
Current Bikes
1969 CB750 Sandcast
1971 CB750K1
1972 CB750K1
1975 CB400F
1975 GL1000 Goldwing
1954 Harley Davidson Panhead
1957 Harley Davidson Panhead
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flyin900
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Re: Piston assembly rear break removal

#19

Post by 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. :-D

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

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
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taunusrainer
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Re: Piston assembly rear break removal

#20

Post by 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
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Joined: Thu Nov 23, 2017 11:45 am
Location: Toronto Canada

Re: Piston assembly rear break removal

#21

Post by 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.
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Current Bikes
1969 CB750 Sandcast
1971 CB750K1
1972 CB750K1
1975 CB400F
1975 GL1000 Goldwing
1954 Harley Davidson Panhead
1957 Harley Davidson Panhead
Prospect
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Zinc Member
Posts: 40
Joined: Thu Nov 23, 2017 11:45 am
Location: Toronto Canada

Re: Piston assembly rear break removal

#22

Post by Prospect »

flyin900 wrote: Fri Nov 26, 2021 8:55 am 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. :-D

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.
Current Bikes
1969 CB750 Sandcast
1971 CB750K1
1972 CB750K1
1975 CB400F
1975 GL1000 Goldwing
1954 Harley Davidson Panhead
1957 Harley Davidson Panhead
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flyin900
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Re: Piston assembly rear break removal

#23

Post by 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.
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
Pb9717
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Location: Loveland OH

Re: Piston assembly rear break removal

#24

Post by 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
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(2) 82' GL1100's
99' Triumph Thunderbird Sport 900
2006 Triumph Speed Triple
Cincinnati OH USA
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flyin900
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Re: Piston assembly rear break removal

#25

Post by 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
Current Bikes:

1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
Pb9717
Cast Iron Member
Cast Iron Member
Posts: 81
Joined: Tue Aug 27, 2019 8:07 pm
Location: Loveland OH

Re: Piston assembly rear break removal

#26

Post by 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.
(2) 82' GL1100's
99' Triumph Thunderbird Sport 900
2006 Triumph Speed Triple
Cincinnati OH USA
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pidjones
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Re: Piston assembly rear break removal

#27

Post by pidjones »

Pb9717 wrote: Mon Nov 29, 2021 2:05 am 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!
"Love 'em all.... let God sort 'em out!"
Ex 2006 GL1800 - the Black Pearl SOLD! to make room for:
2021 Can-Am Spyder RT Limited Dark Chalk Metallic
1975 Red GL1000 project - ex Pistol Pete project
1972 Triumph T150V Trident rescue - finished and FOR SALE!
1976 Yamaha RD400c
1978 GL1000 with '75 engine - the Hunley
Ex 1978 GL1000
Ex 1979 GL1000
Ex '79 CB750F rat bike
Ex '86 SEi
Ex '77 GL1000
Ex '76 RD400
Ex '72 Penton 125 set up for flat track
Ex '73 RD250
Ex '68 TR6C - chopped
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