I wanted to get the front brake squared away before I tried to pull the bike down off the Pink Work Table of Awesomeness. For one, brake calipers are easier to put on when they're not a foot off the ground. Two, this table is no hydraulic uppy-downy type table. No, this sucker's manual-- you push the bike up on an aluminum loading ramp, and take it down using the bike's own functioning brakes.
I already rebuilt the master cylinder, and tested its functionality when I pumped the old brake piston out of the caliper. Once I got the temporary system bled, the MC worked perfectly, and pushed the piston out in about five pumps. Earlier in the thread, I mentioned that I found a reproduction caliper piston on eBay for about $40. I had to wait a long time for it because it got lost in the mail. I contacted the seller, and the new one arrived a couple days later. I had also ordered a caliper seal from Dime City Cycles. I was pleased because it was one of the first parts to arrive. I was sad when I discovered it wasn't the right size.
Next to the piston, it looks pretty close.
Inside the caliper, it's obviously the wrong size.
After doing a little investigating, I found that the OEM part number 45108-300-003 seal is indeed the correct one for a CB650... if it's the European model. American/Canadian models use a different size piston. The European models have a 38mm caliper piston, whereas the American models use a 42mm piston. The correct seal is OEM part number 45215-533-004. I found that using my Custom Google Search-fu here on the SOHC/4 forum, so thank you to those members who have gone before me and figured things like this out!
You can clearly see the size difference. (that's what she said!)
Imagine that... you get the correct size seal, and it fits fine!
A new stainless steel braided brake line, made to my specifications by a guy on eBay. Seems to be of good quality, though it doesn't have the date and country of manufacture. Since I live in South Dakota, things like that are not usually an issue. New banjo bolts and crush washers joined the party soon thereafter.
A new coat of caliper paint in a very high-tech paint booth has everything looking very nice.
While I waited for the new caliper seal to come in the mail, I went ahead and put the MC back on the bike. It still had some fluid in it, so I rigged up the fanciest plug my limited on-hand hardware selection offered. I stacked up a bunch of fender washers and used the banjo bolt to hold them in place. I didn't have another bolt that fit, so this had to suffice. It worked well enough for my purposes, but if you try something like this, expect a few drops of fluid every once and again.
I was still waiting on the stupid caliper seal, so I used that time to finish sealing the blast box. At the end of the night, I looked at my shiny new brake line and thought, "Why isn't this on the bike? It will seal much better, especially with some help from this thoroughly-destroyed inner tube..." What you're looking at is a couple of the small fender washers and a long screw sandwiching a couple small chunks of inner tube around the caliper end of the new brake line. Worked better than the stack of washers at the MC, that's for sure!
I didn't get any pictures of the finished caliper yet because bleeding the system was a frickin' nightmare. I tried for almost an hour to bleed the system, and
nothing I tried worked. Pump and hold, tap the lines to loosen air bubbles, use the jar with fluid and a tube, feather the bubbles out, got a syringe and tried to draw fluid through as well as push fluid up... none of these bleeding techniques worked. I gave up for the night when I noticed brake fluid coming out of the plunger hole. It wasn't much... but enough for me to say f$&% it for the the night.
The next day I tore the MC apart and gave it all another once over, paying special attention to the tiny fluid return hole. I put the whole thing back together, complete with a new o-ring for the reservoir I bought at Ace hardware. No leaks from the plunger, so I think what happened was I pushed the lever too far and some fluid got past the seal. I put the MC back on the bike, filled up the reservoir and lightly feathered the handle. Bubbles galore! Yay! until...
The bubbles stopped. I used zip ties to crack the lever and let it sit all day. Came back... the only resistance I got was the MC spring. Grr... I didn't want to mess with it anymore that night. Turned out the new o-ring was just a smidge too big and let some fluid weep out between the reservoir and the MC body overnight.
Today, I finally got the system to bleed. I took the MC off... again... and cleaned up the holes... again... and put the original o-ring back in the reservoir. It's still weeping, so a new reservoir kit is in my future, I think. I have another MC, so when I noticed the lid wasn't sealing down tight, I got the lid off the spare. Turns out, the reason the first one wasn't sealing was because I hadn't put it back together correctly. There's a metal ring that goes between the lid and the rubber diaphragm, and for some unknown reason, I thought the metal ring went between the rubber and the reservoir. D'oh! Anyways, the replacement fits much more nicely.
Despite the new lid, I still had difficulty getting the system to bleed. Finally, I took the whole hydraulic system off the bike and reassembled it at the bench. Filled it back up with fresh fluid, and still got nothing. I moved the caliper to hang down to the floor. Evidently, I had a huge bubble in the system somewhere, because once I let the caliper dangle, several large bubbles burped up through the reservoir. I stuck a screwdriver between the pads and pushed a little fluid back up into the reservoir. I moved the lever, and I couldn't move the screwdriver. Let off the handle, screwdriver came out. Yay!!
Put it all back on the bike, topped off the reservoir and got ready to move the bike down off the table!!
This is me squeezing as hard as possible.
