Master Cylinder Rebuilding

Now here’s what they sent me:

3F9B2941-7DA2-42AB-86B8-611F6E7093B0.jpeg
 
Looks an awful lot like the first one they sent me, the one that leaked like crazy.

I’m assuming what I pulled out of this mc is probably the OEM Yamaha/Nissin piston (correct me if I’m wrong), and what was in there? Well, it wasn’t the ugliest thing I’ve ever seen, so MAYBE I’d consider reusing it?

Apparently the rebuild kit is Taiwanese in origin, and clearly a different design than whatever I pulled out of my mc.

Now, I’ve owned Chinese dirtbikes: CRF50/XR50 and Z50 clones; I’ve rented and worked on GY6 scooters; to put it bluntly? Counterfeits. With reputable “clones”, that’s what they are: “Clones”. SSR, Zongshen, Lifan, Jailing, etc will line up 100% with Honda parts the vast majority of the time (except for some reason, the main difference is the Chinese use a different shift shaft). Then there’s the “less-reputable” brands, where the engine looks like a Honda, but their guts can be completely different. The GY6 is even worse, but I won’t get into that now. I don’t want to trigger any flashbacks about trying to do a top-end swap in a bathtub.

To make a long story short, I’m thinking this Taiwanese kit might be one of those deals where it’s “loosely-based” on a Nissin mc from an XS650, but “not quite right”? Maybe even a microscopically tighter bore? Maybe they’re just junk? I don’t know, what do you guys think?

The seals on what came out of my mc - for being 40+ years old - still feel hell for stout; while the ones in the rebuild kit feel a bit more flimsy, like the fluid just squirts through when I pull the lever and push the piston in.

Thoughts? Hey, “If it ain’t broke...”
 
here's a (dirty) MC piston setup in order.
mc-guts-jpg.54618


FWIW I seldom buy MC parts, just clean up and reuse what was in there. Has worked for me so far probably 15-20 MCs 10s of thousands of miles no issues. The mostly likely to be dead part is that dust seal on the outside 2nd on left. And yes the daisy wheel should be held captive by a "rivet".
 
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Can you do me a favor (if you still have it out) and measure that piston for me? If not, no worries. The piston they gave me is actually noticeably shorter too, if it isn’t clear from my pics. I should’ve mentioned that.
 
One more thing: The o-ring for the “Standard” Late-Model front reservoir... Does anyone have any idea where I can get one?

For the record, NO, one from a Special won’t work. It’s a totally different reservoir for some inexplicable reason.
 
I 've reused the one that came out. helps to use brake fluid as a lube as you remove the old one. But there's a thread around here where a good fitting o-ring was found, gotta watch material, brake fluid goos some rubbers.
 
Thanks! And I mean the o-ring for the reservoir? Where the plastic reservoir clicks into the metal? Like I said, it’s the “Standard”, not the “Special”.
 
Thanks guys!

My next question: The “Standard” ‘77 front master I bought, does anyone know what submodel it’s from? It’s from a single front disc setup like my ‘80 Special, bolts right up, same line, fitting, taillight switch...

I looked on the Galfer site, and they don’t make a braided line kit for the Special, but now that I put a superbike bar on my Special, the stock front brake line is a good bit too long, and it looks like Galfer has a kit for everything but the Special: XS650D, XS650E, XS650F...

I’d prefer “a bit too long” to “a bit too short”.
 
Machine, little update: Apparently I failed to read the “fine print” on Mike’s XS, supposedly the rebuild kit is for an aftermarket replacement front mc they sell for a Late-Model XS, but they still list it as “fitting” my bike. I just reused what was in my “Standard” mc. No leaks or anything so far. No refund either, sadly...
 
Thanks guys!

My next question: The “Standard” ‘77 front master I bought, does anyone know what submodel it’s from? It’s from a single front disc setup like my ‘80 Special, bolts right up, same line, fitting, taillight switch...

I looked on the Galfer site, and they don’t make a braided line kit for the Special, but now that I put a superbike bar on my Special, the stock front brake line is a good bit too long, and it looks like Galfer has a kit for everything but the Special: XS650D, XS650E, XS650F...

I’d prefer “a bit too long” to “a bit too short”.
70 XS1
71 XS1B
72 XS2
73 TX650
74 TX650A
75 XS650B
76 XS650C
77 XS650D
78 XS650E
79 XS650F
Specials
78 XS650SE
79 XS650SF
80 XS650SG

Even the standard 77-79 line will be a bit long on a superbike bar.
Watch your clutch cable routing, with a superbike bar the cable works best routed on the RH side of the backbone.
 
This will cover the procedure for rebuilding the front brake master cylinder (m/c).
All 3 types will be covered.
There are 3 stock types of front brake master cylinders on the XS650.
The original Round Cover:
insert round assembled here
The "Standard", which has no angle, straight body:
View attachment 7183
And the "Special", which has an angled body to "clear" the Buckhorn handlebars:
View attachment 7184

The inside of the reservoir on all 3 types are also different:
Round Type:
43b8371c15d340bf39b3718c9e24ac94_12799.jpg

The "Standard":
View attachment 7185
The "Special":
View attachment 7186
NOTE: Brake fluid is a dangerous substance. DO NOT let it come into contact with painted surfaces. Immediately clean up any spill and wash hands thoroughly. Keeping a "more than normal" clean area when working with brake parts is very important!
Makes sure you read this in it's entirety and thoroughly before beginning.

To begin, First drain the system using the bleeder nipple on the front brake caliper. Refer to the Bleeding Brakes How-To if you are unaware of the proper procedures to do this. Drain as much fluid out as possible to reduce spillage from the reservoir.
Using the center stand or leveling the bike is a good idea when doing any maintenance.

Open the top cover of the master cylinder after draining the fluid. Put the cover, diaphragm, and diaphragm bushing in a safe place for later inspection/cleaning.
View attachment 7187
View attachment 7188
You can use a rag to "sop" up the remaining fluid. Do not get this fluid on any painted surfaces.

Disconnect the brake line from the m/c. Remove the banjo bolt and 2 washers.
[insert picture]

Remove the 2 10mm bolts from the m/c clamp and remove the m/c from the machine.
View attachment 7189

NOTE:An above average cleaning area is needed for any types of brake repair.

Turn the reservoir 90 degrees to prepare for removal.
View attachment 7190

Using a thin instrument, CAREFULLY raise one corner of the reservoir from the m/c body. There is a large O-ring that the reservoir must be separated from.
View attachment 7191

Work your way around the reservoir to loosen and raise it.
View attachment 7192

Then you can "pop" the reservoir off of the m/c body.
View attachment 7193

You can now inspect the inside of the m/c body and large O-ring. Notice the hardened brake fluid and grime that has collected between the reservoir and m/c body.
View attachment 7194
What size is the O Ring and where can I get one, I ordered one from McMaster-Carr but it is slightly too big and the reservoir won't push in.
 
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