Topic: 400F brakes sticking

[Justind97]

Hi guys,

I've got a 76 400F I've been working on.  For some reason the brakes stick like crazy.

Here's what I've done.

Master rebuild (oem parts, built as per book (I hope it's right))
Caliper rebuild (new seals, piston seemed fine)
New cruisin image brake lines
Ebc pads

When I bolted up the caliper, everything seemed fine.   Then I pumped the brakes a few times to take up any play and the bike would barely move.  I had to push it up my driveway and I swear I've had easier times with cars.

I first blindly put the pads back in as they were before with a nylon shim on the fluid side and the wheel was stuck solid.   Took it apart and discovered that the nylon shim busted apart from age, and was one of the causes of the issue.  I had hoped the issue was resolved, but to no avail.

Now I'm at a loss.

Any idea what would cause this?

[NobleHops]

Hi guys,

I've got a 76 400F I've been working on.  For some reason the brakes stick like crazy.

Here's what I've done.

Master rebuild (oem parts, built as per book (I hope it's right))
Caliper rebuild (new seals, piston seemed fine)
New cruisin image brake lines
Ebc pads

When I bolted up the caliper, everything seemed fine.   Then I pumped the brakes a few times to take up any play and the bike would barely move.  I had to push it up my driveway and I swear I've had easier times with cars.

I first blindly put the pads back in as they were before with a nylon shim on the fluid side and the wheel was stuck solid.   Took it apart and discovered that the nylon shim busted apart from age, and was one of the causes of the issue.  I had hoped the issue was resolved, but to no avail.

Now I'm at a loss.

Any idea what would cause this?

There are two small orifices in the bottom of the reservoir on your master cylinder. The smaller of the two, on the end closest to the brake line, is probably plugged. That's how fluid returns to the reservoir after the brake is pumped. Pluck a strand from a stiff wire brush, clamp it in some needle nose locking pliers, and use it like a drill to clear the blockage. Don't be tempted to put anything larger in there, you don't want to enlarge the hole, only clear it.

In a perfect world you'd do this with it apart so the schmutz could be removed.

[david 750f]

Did the pads move freely in the calipers? Sometimes they need to be "massaged" to fit properly.

[przjohn]

Hi guys,

I've got a 76 400F I've been working on.  For some reason the brakes stick like crazy.

Here's what I've done.

Master rebuild (oem parts, built as per book (I hope it's right))
Caliper rebuild (new seals, piston seemed fine)
New cruisin image brake lines
Ebc pads

When I bolted up the caliper, everything seemed fine.   Then I pumped the brakes a few times to take up any play and the bike would barely move.  I had to push it up my driveway and I swear I've had easier times with cars.

I first blindly put the pads back in as they were before with a nylon shim on the fluid side and the wheel was stuck solid.   Took it apart and discovered that the nylon shim busted apart from age, and was one of the causes of the issue.  I had hoped the issue was resolved, but to no avail.

Now I'm at a loss.

Any idea what would cause this?

There are two small orifices in the bottom of the reservoir on your master cylinder. The smaller of the two, on the end closest to the brake line, is probably plugged. That's how fluid returns to the reservoir after the brake is pumped. Pluck a strand from a stiff wire brush, clamp it in some needle nose locking pliers, and use it like a drill to clear the blockage. Don't be tempted to put anything larger in there, you don't want to enlarge the hole, only clear it.

In a perfect world you'd do this with it apart so the schmutz could be removed.

+2 Your Master has a plugged return orifice.

[chewbacca5000]

I'd listen to these guys they know more about the cb400f than I do.

Now if you want to do a little risk free experiment.  Try this.

Loosen your caliper bolts 2 to 4 turns.  Pump up your brake.  Re tighten caliper bolts.  This should backflush the MC, and there is a small chance it will unplug that return hole.

I do this when sandblasting to clear my nozzle and it works there.

[Justind97]

All figured out.

Turns out the nylon shim that broke apart still had a piece in there.  That fell out when I took the pad out.

I also massaged the pad since it was very tight and impossible to get out.

Thanks for the help!!

[chewbacca5000]

I'd replace those pads or sand the outside so they move freely.  Make sure your brake arm is adjusted properly so your pads don't drag as well.