Topic: '77 CB550F Brakes Too Tight, Too Squishy

[meltshow]

Ah yes, brakes. I've having trouble with the front brake caliper fitting far too snugly to the rotor. I've replaced the piston in the caliper (was pitted) and the rubber ring. I used a wire wheel to clean out the piston (and that groove the rubber ring fits into). It's clean as a whistle. When I reassembled the front caliper after replacing piston, rubber ring and brake hoses, and ran new brake fluid through the master cylinder, the outside brake pad basically traveled all the way until it was clamping down on the rotor. Meanwhile, the brake lever is really squishy, even after bleeding the brake lines. I'm actually back where I was when I brought the bike home: brake pads are too tight, brake lever is squishy/soft. Is the next thing for me to look at the master cylinder?

[meltshow]

Thank you so much for the tip. The first time I bled the brakes, I did see bubbles coming up inside the MC. When you say report unit, do you mean the whole assembly? I'd assume that this is what folks go for: http://www.davidsilverspares.com/CB550F-SUPER-SPORT-1977-USA/part_123898/ over at DavidSilverSpares.com.

[CBGhia]

You might just try cleaning out the master cylinder with a little bit of wire.  Poke the wire into the holes inside of there and see if that helps things. 

Also, have you replaced the brake lines?  They can collapse inside and cause issues like this too.

[meltshow]

The brake lines are brand new. Would I need to disassemble the master cylinder to clean out those holes?

[CBGhia]

The brake lines are brand new. Would I need to disassemble the master cylinder to clean out those holes?

Probably not.  Just fish some slim wire, like thin bailing wire, in there. guitar string would work, too.

[jonda500]

I used a single wire brush bristle held in a pair of pliers...
John

[przjohn]

Did you install new pads with the new piston? Is the caliper piston retracted all the way in the caliper housing?