Scored a cb450 hydraulic front brake set(master, caliper, lines) on ebay for my 550F ss from parts project.
The line splitter that the pressure switch screws into is different but the rest is identical to the cb500/550 brakes. (My 550F currently has an aftermarket master and a cb750 caliper and disc.)
So I have been playing with the master cylinder for 3 days now. First I slipped the caliper over a spare disc, filled the master with fluid and tried my luck with just bleeding it, but nothing at all happened when I pumped the lever. I undid the banjo bolt from the master and tried pumping with my thumb over the hole - still nothing. I carefully poked around in the two holes in the bottom of the fluid resevoir with some fine wire but still couldn't get much to happen except some small air bubbles to come out. I tipped the fluid out and refilled with clean brake fluid a few times during my fiddling and the last time left it overnight with the lever pulled in and tied to the bar.
The next day I pretty much did more of the same - got lots of air bubbles coming out of the two holes this time and when I pulled the lever in I could feel pressure with my thumb over the outlet, however when I let the lever return my thumb was getting sucked into the outlet. I ended the day thinking it was not going to work without rebuilding it and ordered a kit.
Day 3 - I started using metho instead of brake fluid but still achieved nothing but air pushing out and then sucking back in. I noticed the metho kept getting soiled so I kept changing it and also tryed pouring it into the outlet and operating the lever. I noticed that if I shook the metho out (like trying to get sauce out of the bottle) I could entice a lot of crud to come out of the 2 holes - so I kept doing this until I couldn't get any thing else to flush out, then attached it back to a bar, filled it with metho and went back to pumping feeling my thumb get pressed outward then sucked back in. Then gradually I started to get a small amount of metho coming out with the pressure on my thumb and realised after a while that if I pulled and let go of the lever and then waited a few seconds, the vacuum pulling on my thumb went away by its self which let me have lever pressure to pump again and WOOO HOOOOOO metho squirted out!!! - I still have to wait a second between letting go and pulling in the lever, but I have flushed, refilled and bled the system and have a remarkedly firm brake lever. I am glad I haven't fitted the parts to my bike yet though as the caliper is now firmly stuck on the disc with a vice like grip and the new piston & seal that I ordered haven't come yet. (now really wishing I didn't also order a master cylinder kit!)
