82 GL1100 rear master cylinder rebuild

[Explorer]

As a part of my on-going rebuild I wanted to replace the innards of my rear master cylinder. It turned out that the one I had was not in a condition to be worked on, the snap ring although still in place was rotted away, meaning there was nothing to grip on to get it out, also the screws that hold the plastic fill union in place had been wallowed out, probably by someone trying to use a Phillips screwdriver.
I took a risk in buying it, because I know these things just don't turn up every day, but I got real lucky on eBay.
This one has none of the problems I had before, it appears to have cleaned up real good so far and it is even the right size bore for my Interstate running an Aspencade rotor.
My question for you guys is this though? I managed to get 1 copper strand out of a #12 wire down the tiny return hole. is this enough? It was not a fluke, as I was able to repeat it several times, but is that sufficiently wide enough to reliably call this a good cylinder?

[10mm Nut]

I just did mine a week ago. Same bike, 1982 model. The compensator port is tiny, but it was big enough to get a tiny drill bit through it.



You can see the little set of drill bits in the picture. I used the white one in the center of the set.

[Explorer]

The one in the middle of the set? Wow, that's much wider than what I got in there. I think what I had was about the size of the small white drill.
By the way, your stuff is in way better condition than even my new stuff is!

[10mm Nut]

I guess I should have given more details. My master cylinder was a hopeless eBay 25 dollar special. It was seized tight. It took a lot of effort and time to get it apart and cleaned up. It soaked a long time in Evaporust and then did several cycles in an ultrasonic cleaner. But the internal parts you're seeing are the new parts from the rebuild kit. The master cylinder body and pushrod are the only used parts in that picture.

But, for the drill bit, let me correct myself. It was the black one near the middle of the set. A compensator port is one place where if you were to slightly oversize the orifice it wouldn't affect anything. It's purpose is to allow the backflow of fluid and bleed off the return pressure. Upon applying the brake, once the internal piston strokes past the hole it is no longer in play until the pedal is released again.

I found a picture of the bit I used.



But to start with it was a hot mess. I eventually had to center drill the old piston and use a screw extractor to get it unstuck from the bore.

[Explorer]

I appreciate and understand the work you had to do get it where it is but what I was looking at of yours was the snap ring groove, it looks pristine, unfortunately I don't have access to an ultra sonic anything, I did the best I could to mine in regular de-greasing fluid and a bunch of scrapers and picks. It's nice to know though that someone just a few hours away is going through the same thing I am, and thanks for your insight into the hole not having to be the exact right size. Also where did you get that drill/driver set?

[10mm Nut]

The drill bits are part of an Amazon set. Cheap. Like 13 bucks.

https://www.amazon.com/gp/product/B07Y3 ... UTF8&psc=1

Where are you at in Texas? I'd be happy to ultrasonic parts to help a fellow nut.

Will trade ultrasonic work for toilet paper (Coronavirus joke)....

Too soon ?

[Explorer]

I finally got it.

Thank you for your offer though.

Not the virus, the master cylinder.

At least, so far.

[Sidecar Bob]

FWIW, I usually use a sewing needle to clear the return hole.