Master Cylinder

Chrisraven

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I am trying to get the master cylinder reservoir off the base. It is the plastic one with the 4 screws to hold it in place. I removed the 4 screws and tried to pull it out. It will rotate quite freely but it refuses to come out. It looks like there is two rubber "O" rings or seals that is holding the throat of the reservoir on.

I would like to rebuild it just because there was a significant pile of crude in the caliper and the hose is plugged solid. The plunger works in the master cylinder but I think there is something in there that is not operating right. It has been sitting for lots of years.

Anyone know if the reservoir just pulls out? Albeit hard I tried a couple of flat scrappers to try some leverage and still not reaction. It flexes up but not releasing from the barrel of the base.

Thanks
 

amc49

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Don't be surprised if it breaks, some do. Sometimes the o-rings get hard as rock and will not deform to peel loose.
 

amc49

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Yes, it would have taken little effort to pop it in when new and o-rings soft. The same problem with lots of car reservoirs now too, made to pop into place and you blast to remove them later. It makes buying a new automotive M/C less reservoir very problematic
 

mpfalcone24

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So am I right, that it does just pull out without anything else but the "O" rings holding it in?

It’s just a single O ring and yeah they are a bear to get out when they are older...

My 1980 took two pry bars to get it off...thankfully it didn’t break!


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Chrisraven

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I'm going to give it a go again with my prybars, I tried last night but it did not budge so I looked on line to see if I could get a replacement and they are available from Vintage CB, so if it breaks no big deal....lol
I'll let you know how it goes
 

pidjones

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Patience, heat, screwdrivers for wedging and levers. Did I mention patience? And when you get it off, don't bypass cleaning the "spluge" hole - tiny hole in the bottom that releases pressure when you release the lever. Otherwise, the brakes will stay locked. I use a piece of high "E" string from an electric guitar set chucked in a pin vice. Cut at an angle, it can drill through the buildup. I hate brakee.
 

amc49

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My favorite tool to hone the M/C interior out is a piece of all thread maybe 5 inches long chucked in a drill and split on the end right in the middle with hacksaw maybe 1/2"+ deep. Then fold up a piece of #400 sandpaper 2 inches long X 1 inch wide one time lengthwise to make hone blade 1/2 X 2 inches long double layer, abrasive side out. Next stuff that centered up, fold facing forward, into the all thread slot to make a flapper wheel that makes a fantastic cheap hone that easily goes into the M/C bore. Hone the bore using lube, like oil cut heavy with fuel to make a honing solvent that floats away crap to keep the sandpaper clean. Use a never stopping in/out action to even the honing out and not dig into one spot. Clean the bore and look at it with the end open to the sun and looking for water damage to make low spots that don't get touched by the hone. If you got that the cylinder will likely leak when rebuilt, you need all or very little of the damage left gone to make one that seals well.
 

Chrisraven

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Finally got the brake fluid take off the frame, had to pry it out with a foot long screwdriver. Turns out the is a recessed ring on the tank that is chamfered so the tank goes in fairly easily but when removing you have to get that ridge over the "O" ring, once a part of it goes over the "O" ring then the rest comes out really easy.

Cleaned out the pin hole, it was plugged up with crud, open now so that's a good thing.

It looks like the bore is good, just used brake clean and a rag that I twisted through the bore. Bright and shiny, but will get my magnifier lens in there and check for any pits. Hopefully it will come out fine and I can just rebuild it.

Thanks for the input.
 

amc49

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It's pretty unusual to have a perfect bore, most will have something pitted in there if bike has sat.

Regarding the pinhole, you should have TWO holes there, one bigger and the very small one.
 

Chrisraven

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Yes I have two holes, the big one was an easy clean, not so easy on the small one, used a number drill in a pin drill to cut through some of the crud and then put the .009 thou wire in the pin drill and got that small hole nice and clean.

There are some marks in the bore but I think it should be good.

You wouldn't know the official colour of the 1980 CB750 C would you? So far all I have found is Candy Muse Red, I'm going to take it to a body shop that has a camera and we are going to scan it to see what I can come up with for a colour.
 

Chrisraven

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Yes mine is an 80 it has single disk on the front. The colour that I have is a deep colour and I have found "Candy Muse Red", For sure it is not Black. Thanks for your input
 

mpfalcone24

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Yes mine is an 80 it has single disk on the front. The colour that I have is a deep colour and I have found "Candy Muse Red", For sure it is not Black. Thanks for your input

040f79c685323e1787e55f8002e844ed.jpg

Here is mine and it is the candy muse red...it’s more of a maroon...


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Chrisraven

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Hi mpfalcon24: Perfect that is the exact bike that I have. Could you possibly do me a favour and take a picture of the warning decal and the Custom decal on the tank please. I have been trying to find these so I can get the decal made locally. Or do you know where I could get the decals for the tank by chance? I just noticed that looks like a decal on the chrome chain guard, is there one there or is it just reflection on the chrome?
I can get you my e-mail address if you want to send me a higher resolution picture of the decals if you like. There must be some way we can message more securely to give members more personal information rather than on the open forum. By the way I am on Signal.

Thanks for you input, this is great news now I know for sure I can track down the paint mix.

Chris Raven
 

Chrisraven

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Hi mufalcon24, I just talked to the paint guy and he said that the paint code number is usually under the seat on these bikes. Any possibility of you having a look under the seat and see if there is a paint number there? I would really appreciate that.

Thanks
Chris
 

mpfalcone24

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Hi mpfalcon24: Perfect that is the exact bike that I have. Could you possibly do me a favour and take a picture of the warning decal and the Custom decal on the tank please. I have been trying to find these so I can get the decal made locally. Or do you know where I could get the decals for the tank by chance? I just noticed that looks like a decal on the chrome chain guard, is there one there or is it just reflection on the chrome?
I can get you my e-mail address if you want to send me a higher resolution picture of the decals if you like. There must be some way we can message more securely to give members more personal information rather than on the open forum. By the way I am on Signal.

Thanks for you input, this is great news now I know for sure I can track down the paint mix.

Chris Raven

15e06f840ba1bd6983681cead4ba85bd.jpg



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mpfalcone24

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Hi mpfalcon24: Perfect that is the exact bike that I have. Could you possibly do me a favour and take a picture of the warning decal and the Custom decal on the tank please. I have been trying to find these so I can get the decal made locally. Or do you know where I could get the decals for the tank by chance? I just noticed that looks like a decal on the chrome chain guard, is there one there or is it just reflection on the chrome?
I can get you my e-mail address if you want to send me a higher resolution picture of the decals if you like. There must be some way we can message more securely to give members more personal information rather than on the open forum. By the way I am on Signal.

Thanks for you input, this is great news now I know for sure I can track down the paint mix.

Chris Raven

6900adb641935b3829a86e531f71c4b9.jpg

Chain guard decal


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mpfalcone24

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Hi mufalcon24, I just talked to the paint guy and he said that the paint code number is usually under the seat on these bikes. Any possibility of you having a look under the seat and see if there is a paint number there? I would really appreciate that.

Thanks
Chris

a775c05a24a18927d8781f698176910b.jpg

Here’s what’s under the seat! Best of luck!


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