Topic: Front Brake Dragging - '75 CB550F

[TedH]

OK.  After bleeding the front brake several times and having the impression the bike was rolling with less resistance... I'm back with a rotor that flashes water to steam (squirted on the rotor) after less than a 2 mile ride. 

Some background:

Bike purchased, picked up Tuesday this week.  Found the bike did not want to roll easily when just dropping it off the center stand or even just wheeling it around the garage.  Then, after a ride, it was almost as if I was engaging the front brake.  So, I bled the front system... 3 times.  Each time, it 'felt' as if it was freeing up. 

Yesterday, I also decided to check with PO regarding what felt like a 'wobble' in the front wheel.  I took a closer look and found a strip of weights.  PO says they were there when he bought the bike.  He didn't remove them when he installed the fresh Michelins to the front/rear.  Well, I removed the adhesive strip of weights and the wobble is now gone. 

But, my front brake is dragging!!!    Looks as though I'll have to tear the front brake off and clean/inspect.  I hope that the worst it will require is a rebuild kit.  PO says he rebuilt the front master cylinder, installed new brake line(s) and installed BMW crush washers in place of the $3 Honda washers where the brake line meets the master cylinder. 

The rotor appears flat/true and has no grooves.  It is just getting very hot from the brake dragging at speeds. 

[Duke McDukiedook]

Sounds like he avoided the most important part of the rebuild- the piston seal.

Change that out and I am pretty sure your sticky situation will be sticky no more.

Check out the brake faq for details on the rebuild.

[flybox1]

Sounds like he avoided the most important part of the rebuild- the piston seal.

Change that out and I am pretty sure your sticky situation will be sticky no more.

Check out the brake faq for details on the rebuild.

+1

bleeding the system only adresses filling the lines and clearing bubbles.
it wont get all of the sludge & old brake fluid out.
disasemble the caliper, get a new pistson seal, and possibly a new (phenolic) piston, if the one in there is pitted.  while in there, check the pads for wear, and see if you need new. be sure to get the piston seal groove really clean.  simple green soak with a brass or hard plastic bristle wheel attachment on a dremel is money for this job. refill and bleed, bleed, bleed.

[TedH]

Good advice all.  I'll tear the front caliper down this afternoon to see what I'm dealing with.

[flybox1]

DOT 3 eats paint.

[Duke McDukiedook]

Order a new piston seal first.

[Deltarider]

Watch for the right orientation of the seal. Usually the rim of the rubber seal is a little bit higher on one side. That side should be on the diskside. It will help to retract the piston immediately after braking.

[TedH]

PO is shipping a gasket set.  May be for engine... he is not sure what is included (?).  I'll tear it down and decide on what I need to do.... I have to other bikes I can ride (550K and Yamaha triple), if the weather is nice

[CB500_k2]

Make sure that you have a little slack between the disk and the static pad on the caliper.  Getting just the right setting on the caliper adjustment bolt takes a bit of finesse.