Topic: 350F brake caliper won't retract

[Jay B]

I put a rebuild kit in my master cylinder and now the front brake seems to bind. The caliper isn't retracting as it should. The caliper piston is nice and free so that's not it. When I rebuilt it I installed both seals with the "open" ends towards the outlet. This MC was really gunked up. I've got one open hole from the resivore to the bore. There is also a divot cast into the bottom of the resivor, like another hole that doesn't seem to go through. Should this be open? This thing totally binds. To test I loosened the bolts that hold the caliper together, pumped the piston out a little and gently tightened the bolts. The brake locks solid and the lever gets rock hard. I let it sit for a couple hours and the pressure didn't back off. Even after bleeding the wheel will hardly turn by hand. Any ideas? BTW I did searches and stuff and didn't come up with an answer.

[Bob Wessner]

There is also a divot cast into the bottom of the reservoir, like another hole that doesn't seem to go through. Should this be open?

The divot you refer to, looks like someone started, but did not finish the hole?? If so, yes, there is a v-e-r-y small hole at the bottom. I had to clear mine, and take it out in direct sunlight to see that is was cleared.

[Jay B]

Thanks Bob, Yep, that's what it looks like. I'll clean it out over the weekend.

[Hockers Choppers]

Make sure the rubber plunger is the same as you old one. I had a kit with the wrong one and it wouldn't allow fluid back thru because the skirt was to long on it.

[tomkimberly]

There is also a divot cast into the bottom of the reservoir, like another hole that doesn't seem to go through. Should this be open?

The divot you refer to, looks like someone started, but did not finish the hole?? If so, yes, there is a v-e-r-y small hole at the bottom. I had to clear mine, and take it out in direct sunlight to see that is was cleared.

If you have a True Value Hardware store in your area, they sell a small pin vise with a wide assortment of very small drill bits enclosed in the handle, these work very well to open up these type of passages.

Tom

[Hockers Choppers]

There is also a divot cast into the bottom of the reservoir, like another hole that doesn't seem to go through. Should this be open?

The divot you refer to, looks like someone started, but did not finish the hole?? If so, yes, there is a v-e-r-y small hole at the bottom. I had to clear mine, and take it out in direct sunlight to see that is was cleared.

My 78 cb750f's rear master has a similar hole that looks like it didn't get drilled all the way out. Did this one also have the really tiny hole? Mine seems to bind like this sometimes. I've cleaned the bore twice but didn't know there where two holes.

[Bob Wessner]

There is also a divot cast into the bottom of the reservoir, like another hole that doesn't seem to go through. Should this be open?

The divot you refer to, looks like someone started, but did not finish the hole?? If so, yes, there is a v-e-r-y small hole at the bottom. I had to clear mine, and take it out in direct sunlight to see that is was cleared.

My 78 cb750f's rear master has a similar hole that looks like it didn't get drilled all the way out. Did this one also have the really tiny hole? Mine seems to bind like this sometimes. I've cleaned the bore twice but didn't know there where two holes.

I can't say for sure, but if it looks like that, good chance. Try poking a very thin wire through at the bottom.

[Bob Wessner]

Actually, as I recall, I cleared the one on my front M/C using the tip of a sewing needle.. that's how small the hole it. Let us know what you find.

[kghost]

Plucked a peice off a brass brush and stuck it in the hemostats. Seemed to do the job.

[Hockers Choppers]

Hey Bob,

Yes, I took the m/c apart again today (4th time ) and it looked like the second hole was just not drilled out. Tried poking it with a small o ring pick and no deal. Tried a VERY small drill bit from a cutting torch cleaning set and used the smallest bit ( almost micro scopic ) and it drilled out the crap!!!! works perfect now !!???!!!??? I can't believe they made the damn thing like that. Anyway it works now and I'm very happy.

Thanks again for the advice, I never would have thought there was a second hole in there.

Jesse

[Bob Wessner]

Glad to hear. Happy stopping.