Hydraulic rear brake master cylinder rebuild kit?

Is there a Napa number?

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flatheadDave
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Hydraulic rear brake master cylinder rebuild kit?

#1

Post by flatheadDave »

My master is leaking and I’d like to do a rebuild hopefully with some parts at my local auto shop. Does Napa or Autozone or Oh Oh OReilly’s have any parts that would be compatible for the Wagner rear brake master cylinder?
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Re: Hydraulic rear brake master cylinder rebuild kit?

#2

Post by RooDog »

Find a cup marked 3/4 inch, and an o-ring that fits the piston, and go for it....
You could also probably use the cup & )-Ring from a 1972-84 handlebar master cylinder.
All this is pending if the other metal internals are OK, and the bore only needs honing....
....RooDog....
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Re: Hydraulic rear brake master cylinder rebuild kit?

#3

Post by flatheadDave »

Ah ok! I have plenty of sizes of o rings so that’s good. What’s the best way to home the bore? It’s so fing tiny.
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Re: Hydraulic rear brake master cylinder rebuild kit?

#4

Post by RooDog »

You could use a brake cylinder hone.....
I bought mine about 50 years ago....It's a life time investment....Or not?

https://www.supercheapauto.co.nz/p/tool ... 12572.html
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Re: Hydraulic rear brake master cylinder rebuild kit?

#5

Post by PanPal »

I had to use one like Roo posted that had worn out stones. A new one would not fit in the bore. I also add a washer before putting in the locking ring to relocate the spool inward slightly. Normally there are pits that can cause brake fluid to leak when the spool sits retracted. You do need to make sure the spool still retracts enough to clear the hole in the reservoir.
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Re: Hydraulic rear brake master cylinder rebuild kit?

#6

Post by RooDog »

There are also hones with just two stones for smaller bores like on out motorcycles.
An example:

https://www.fleetfactors.co.uk/consumab ... 4mm-p19409

PS: Do Not Use A Stone Hone in an Aluminum MC. They tend to load up and gouge the bore....
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Re: Hydraulic rear brake master cylinder rebuild kit?

#7

Post by Wrong Road »

A ball hone does a great job on the master cylinder. I posted some pictures of one that I used on my '60 but can't find them in the forum.
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Re: Hydraulic rear brake master cylinder rebuild kit?

#8

Post by Chief3Kicks »

My brake cylinder stone-hone I've used on cars for 30 years wouldn't quite collapse small enough to fit the panhead MC so if you buy one, make sure of the minimum size it will do.
I'm sure I'll get rolled eyes over this but I wrapped a ball of 000 Steel wool on a 3/8 drill bit and with some oil and careful working, cleaned it up nicely. Really a hone is just freshening/smoothing up the surface on these anyway. Not like an engine cylinder where rings must seat under high compression and heat. If its in such bad shape that you need more than a clean up, it should be replaced. After the steel wool I put polishing compound on a rag and gave it the same treatment. Probably nicer finish than repops from China
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Re: Hydraulic rear brake master cylinder rebuild kit?

#9

Post by nifty »

Ditto for a hacksaw split in a piece of steel rod, strips of emery tape wound to size so it just goes in, drive with a power-drill.
Wind the correct direction and don't start drill until emery tape is inside bore, after a few passes stop drill before removing from bore.
If you hone wet, use brake fluid, water, or alcohol.
There are auto brake specialty shops who re-sleeve OE cylinders with brass or stainless.
Nifty
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Re: Hydraulic rear brake master cylinder rebuild kit?

#10

Post by panhead_kicker »

flatheadDave wrote: Tue Nov 16, 2021 7:15 pm ... Does Napa or Autozone or Oh Oh OReilly’s have any parts that would be compatible for the Wagner rear brake master cylinder?
Dave,
I think both VTWIN and CCI have them.
F71670, WK71670
F71670, WK71670
IMG_5087.JPG (154.55 KiB) Viewed 430 times
But as you can see, they are simply resold , Wagner / Federal Mogul. Heres the part number to ask for:
41748-63 = F71670, WK71670
41748-63 = F71670, WK71670
41748-63 = F71670, WK71670
IMG_5089.JPG (143.99 KiB) Viewed 430 times
As far as honing, NAPA has a nice hone set I've used for this purpose several times:
IMG_5085.JPG
IMG_5085.JPG (182.7 KiB) Viewed 430 times
IMG_5086.JPG
IMG_5086.JPG (218.71 KiB) Viewed 430 times
nifty
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Re: Hydraulic rear brake master cylinder rebuild kit?

#11

Post by nifty »

Pay attention to the instructions on the CCI/Wagner packaging, re only DOT 3 brake fluid.
Not all brake seals, o-rings and hoses are compatible with DOT 5 fluid and the incompatible ones can swell/fail prematurely/catastrophically.
Nifty
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Re: Hydraulic rear brake master cylinder rebuild kit?

#12

Post by panhead_kicker »

panhead_kicker wrote: Thu Nov 18, 2021 8:50 pm
flatheadDave wrote: Tue Nov 16, 2021 7:15 pm ... Does Napa or Autozone or Oh Oh OReilly’s have any parts that would be compatible for the Wagner rear brake master cylinder?
Dave,
I think both VTWIN and CCI have them.


But as you can see, they are simply resold , Wagner / Federal Mogul. Heres the part number to ask for:
41748-63 = F71670, WK71670
Sorry Dave ! I just realized you wanted the Master cyl. rebuild, but I gave you the wheel cylinder rebuild. I do not have a Wagner number for that. I purchased several $5 India made kits off Ebay to try.
# 41762-58 Been running one with no issue since 20-Jan-2021.
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