brake master cylinder ...next after circlip & screw out?

I've got a complete M.C. rebuild kit, and started to pull the master cylinder off the bike, but I'v run into a point where I don't quite understand what the books said, or the couple of threads I found on the forum. Probably because I do better with visuals than words.

I've taken out the circlip at the top, the float that was under it, and the screw off to the side. I stopped before I did any more damage. I thought it pulled out, and now there are a couple rough spots on the little top rubber piece by letter A in the pic below. It's currently still attached to the bike by the wire underneath. i assumed that wouldn't come off until I removed the circlip and float, then pushed down. I was wrong, apparently.

Where I'm at now:

 

The entire sensor unit/wire harness comes out thru the TOP of the reservoir. There is an o-ring on the bottom of the shaft that fits into the passage hole (prevents brake fluid leaking out thru the wire passage hole) and this o-ring can swell and "seize" the assembly in place. You can try shooting some solvent/silicone into the hole (from underneath) and let it penetrate for a few moments/hours and try again. It may take a bit of minor "twisting" action of the sensor shaft assembly to break the o-ring free, and then it will push out more easily.

 

You ain't kiddin! Squirt some silicon on the bottom. Wait a half hour. wiggle wiggle. no luck. wait. repeat. I'm at the 2 hour mark now. looks like the o ring might be spinning around in there, but still not budging!

Just in case I mess up that sensor going into it, is it replaceable?

 

update, and follow-up question: finally, after three hours of soaking with silicon, and pushing at it with a small dull eyeglass screwdriver, it pushed through.

But... forgive a dumb question: How do I get the master cylinder housing off that sensor? does that plastic end come off, or do I need to disconnect the wire from the instrument panel? I've been perusing the instructions I can find online, but none of them seem to show this part of things (or the pictures are broken)...I just wanna be sure before I do any more damage. Here, in this photo, you can see I've already dinged up the sheath on the wiring.

 

Pull out your headlight and trace the wires to the correct connector to disconnect. You may have to take the wire cover off your buckhorn to release the wires. Don't do like I did and accidentally unplug the wrong connection because their are a couple in there that look the same.

 

A new question... but I'll post here to avoid unnecessary extra Master Cylinder posts.

I got my master cylinder off last weekend. Through the week, I took everything apart... and found some pitting inside the piston bore. Generally it looks pretty smooth, but there's pitting toward the back, close to where the pinhole (relief port?) comes into the cylinder bore. I've got a dowel and some 1200 grit sandpaper, so I might try that... but is this far enough back that that it's won't cause any problems? I don't think it's far enough back, just eyeballing it, but wanted to see what others said.

Edit: just realized I should clarify the pitting is on the opposite wall of the bore from the pinhole

 

If the pitting is beyond the area that the piston seal has to sweep, then there won't be any issues.

 

hmmm... seems to be right at the edge of the piston sweep. might be just beyond, but I'm not sure.

On a whim, I stopped at Bob's, a local boneyard and got a master cylinder off an '85 or so Virago (700). Looks the same, but doesn't have the opening for the low fluid sensor.

Not sure it'll work for this though, and I prefer to keep things as original as I can.