Piston assembly rear break removal

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Prospect
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Piston assembly rear break removal

#1

Post by Prospect »

The rear break piston assembly is stuck. I would expect that when I removed the pushrod it would pop out. That would happen when the bike was new. I'm soaking it in PB blaster overnight but I doubt it will do anything.

Any tricks to get it out?
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pidjones
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Re: Piston assembly rear break removal

#2

Post by pidjones »

Sometime the masters get pretty gummed-up. You may need to force it out with air or even hydraulic pressure. If it is open on the other end, you can use a rod to force it out.
"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
Prospect
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Re: Piston assembly rear break removal

#3

Post by Prospect »

pidjones wrote: Wed Nov 10, 2021 9:27 pm Sometime the masters get pretty gummed-up. You may need to force it out with air or even hydraulic pressure.
Yup. I was hoping there was a simpler way. The mounting bolt is usually positioned opposite the piston and you can force it out that way. I see that on the gl1000 there is a 90 degree angle so that's not an option.
Current Bikes
1969 CB750 Sandcast
1971 CB750K1
1972 CB750K1
1975 CB400F
1975 GL1000 Goldwing
1954 Harley Davidson Panhead
1957 Harley Davidson Panhead
MattMcCoy
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Re: Piston assembly rear break removal

#4

Post by MattMcCoy »

I got a stubborn one out pretty easily using a grease gun.
1983 GL1100A Aspencade
1977 GL1000
1978 GL1000
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flyin900
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Re: Piston assembly rear break removal

#5

Post by flyin900 »

I use compressed air and it sometimes works on removing the parts. They get stuck from old crystalized or gummy fluid. When you do get it out the tiny spooge hole in that body where the line from the master reservoir connects to the block needs to be verified as open and cleaned too. Just like a upper master for the front brakes, both have a larger and very tiny hole in there.
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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tomk1960
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Re: Piston assembly rear break removal

#6

Post by tomk1960 »

I have had to deal with this many times when prepping a master for powder coating and have a good trick for getting stubborn pistons out. Clamp the part in a vice (using some wooden blocks to protect the casting) with the piston end pointing up. Now use a punch to tap the piston in deeper, in order to break it loose. Sometimes that will be enough to allow you to blow it out with compressed air. If not, then drill a hole part way into the top of the piston. Then turn coarse threaded drywall screw into the hole nice and tight. Often the piston will start to spin when the screw bottoms out. After that happens, just turn the screw and pull as you turn. Worst case, you can grab onto the screw head and pull out the piston.

If this procedure doesn't work, my last resort is to pump out the piston hydraulically. This always works.

This procedure assumes you're doing a proper rebuild and will be using new master cylinder kit, which includes a new piston.

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1986 VFR750F Interceptor
1983 Honda CB1100F Super Sport - Red 1123 Resto-Mod
1978 Honda GL1000
Prospect
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Re: Piston assembly rear break removal

#7

Post by Prospect »

I soaked the piston assembly overnight in PB blaster. I then used my compressor and the piston flew out across the garage. Rookie mistake but I didn't think it would work so I didn't put a cloth to catch the piston. I managed to find all the parts and cleaned everything using brake cleaner and compressed air. The rubber parts on the piston assembly looked in really good shape so I used them again. I lightly honed the bore and lightly cleaned the side of the piston for easy movement. I tested it out on the bench and the assembly moved freely.

However, when I put everything back when I actuated the brake pedal it was slow to return. I wasn't getting any bubbling in the master cylinder and no fluid was flowing. Disappointed.

I'm hoping to buy from Honda just the rubber pieces but it looks like they don't sell them individually but rather as a whole piston assembly. I don't trust aftermarket brake parts. I've had them leak on me before. Is there a source you trust?
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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tomk1960
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Re: Piston assembly rear break removal

#8

Post by tomk1960 »

I've been using K&L brake rebuild kits for years and have never had an issue. The parts that Honda sells are sourced by the same manufacturer that K&L uses - Nissin.

I don't care how good the internals look - if they were so stuck that it took compressed air to dislodge them, it's time to replace. Cheap insurance.
1986 VFR750F Interceptor
1983 Honda CB1100F Super Sport - Red 1123 Resto-Mod
1978 Honda GL1000
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flyin900
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Re: Piston assembly rear break removal

#9

Post by flyin900 »

tomk1960 wrote: Thu Nov 11, 2021 9:05 pm I've been using K&L brake rebuild kits for years and have never had an issue. The parts that Honda sells are sourced by the same manufacturer that K&L uses - Nissin.

I don't care how good the internals look - if they were so stuck that it took compressed air to dislodge them, it's time to replace. Cheap insurance.
+1 on the above!

Buy the kit as noted then everything is new in there. Did you also confirm the small return hole I indicated in my earlier post was clear? This is where the return pressure is released in the system when you release the brake pedal/lever. If this is not clear the brakes can drag, or you may experience that symptom you noted in your post.
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

#10

Post by Prospect »

I found a Canadian supplier that sells the K&L brand. I'll order it 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
Prospect
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Joined: Thu Nov 23, 2017 11:45 am
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Re: Piston assembly rear break removal

#11

Post by Prospect »

The kit arrived. I unscrewed the two Phillips screws inside the reservoir but I couldn’t get the reservoir off. I don’t want to break it.
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

#12

Post by flyin900 »

Prospect wrote: Fri Nov 19, 2021 10:47 pm The kit arrived. I unscrewed the two Phillips screws inside the reservoir but I couldn’t get the reservoir off. I don’t want to break it.
Ok it seems both the front and rear master cylinders use the same set up for the reservoir design. That plastic cup has an O ring that seals it around the aluminum base. Over time dried brake fluid locks it in there pretty tight.
You can try soaking it in hot water to help dissolve the crud and then rotating it helps break that seal. If you then can get an edge up and started a large flat blade screwdriver helps pry it off.
My experience is once you break that seal the odds of it not leaking again around there if you don’t replace that O ring are 50/50. Honda used to still offer that O ring as a replacement part.
Again check that very small return hole down in the base, as that will cause the brakes to drag, or possibly your issue with the brake lever slow to return.

That O ring is 43.7 OD X 2.5 CS in size and part 45516-371-003 - In short to NLA supply is seems. A size 44 X 2.5 will likely sub if needed.
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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pidjones
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Re: Piston assembly rear break removal

#13

Post by pidjones »

Yes, you must remove the reservoir, and flyin900 describes the process well (the hot water really helps). There are several threads on here that show and describe what some call the "splooge" hole. It MUST be opened up. I used a high E electric guitar string in a pin vice to open them and healthy shots of brake cleaner to insure clean and free-flowing. The hole is tiny and often in a depression that appears to have no hole at the bottom. With plastic reservoirs, it is often under the plastis to prevent back-spashing on release. More modern MCs have a litgle thin plate over the hole.
"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
Pb9717
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Re: Piston assembly rear break removal

#14

Post by Pb9717 »

pidjones wrote: Tue Nov 23, 2021 8:17 am Yes, you must remove the reservoir, and flyin900 describes the process well (the hot water really helps). There are several threads on here that show and describe what some call the "splooge" hole. It MUST be opened up. I used a high E electric guitar string in a pin vice to open them and healthy shots of brake cleaner to insure clean and free-flowing. The hole is tiny and often in a depression that appears to have no hole at the bottom. With plastic reservoirs, it is often under the plastic to prevent back-spashing on release. More modern MCs have a little thin plate over the hole.
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.
(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

#15

Post by pidjones »

On the rear it is sometimes behind a blank bolt that seems to have no purpose. Look carefully behind it and you will find the depression, then try for the hole.
"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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