Topic: '74 CB550 Master Cylinder question...

[Airbusboy]

HI guys... When I acquired this bike it hadn't run in 38 years. It was parked with gas in the tank and brake fluid in the front system. All of it dried up and has been a major pain to clean out. I THOUGHT I had the front brake system cleaned, filled and bleed but on the first test drive I found the front caliper sticking. I KNOW it is clean and I highly suspect I didn't get the return hole cleared. When I look in the bottom of the reservoir I see two holes. One (furthest outside to right of bike) is clear and I can see the piston assembly move when I squeeze the brake handle. The other hole doesn't appear to be clear. It actually appears not drilled all the way through. Is that possible? Should it be open into the piston cavity? Is this the return hole and if not, where is it? When I cracked the bleeder open the pressure was relieved and the front wheel turned free. I also installed Galfer SS lines all the way around and cleaned out the manifold. Suggestions?

[Scott S]

 That hole should be open but is very tiny. Use a pin or small piece of wire and see if you can clear it. Maybe try moving the piston with the lever while doing it so you can feel the wire poking through.

[bryanj]

Use the search function and look at the pictures other people have put up

[Johnie]

Yes, that hole you are talking about is the return hole. It is sooooooo small that I use a single strand of wire that I pull out of my wire brush to clear it. They say the E sting from a guitar is a perfect fit too. You will probably need to rotate the wire while gently pushing to clear it.

[lucky]

Right here.
I posted it on the other thread too.

[Airbusboy]

Thanks guys....I'll hit it tomorrow and see if I can clear it.

[Airbusboy]

BINGO!  Yeppers....looked good and no hole. So I used a needle and she did indeed open. Took her on a test run and the front brake functions perfectly!  Thanks to all for the help!  Now I just need to get that disc looking new again instead of heat-blued and I'll be happy.....