85R Rear Brakes Problems...Please Help

[Red Rider]

Are you running an OEM brake disc or aftermarket? If aftermarket, what is the thickness of it?

[Onetrackmind]

I'm not sure if it's the stock disk or not. It is measuring about 3mm thick though.

I put the old pads back on (which still had some life left in them) hoping that would solve the clearance issue and it looked good until I depressed the brake lever. The Pistons extended and did not fully retract. Is this now a master cylinder issue?

Also when I go to push the Pistons back in they move freely, but only one at a time. When I push one in, the other pops out the same distance. I'm not the sharpest knife, but I'm not dumb either...but this is making me feel like a complete idiot.

Thanks.

[Slingblade]

If you've got the system completely full of fluid, you will have to let off pressure. Crack the reservoir cap, bleed screw etc. Put an old brake pad accross both pistons and use a c-clamp or pliers.

It sounds like your caliper is working correctly. Like everyone said, the pins that let it float on the disc are almost always the culprit. I have destroyed good calipers trying to un-freeze them.

Let off pressure, push pistons in. Put in pads, bolt up caliper and bleed, then bleed again, and maybe again. Brake systems hate air.. Then I think you'll be good.

[Onetrackmind]

Thank you, thank you, thank you guys for all the help! I did just that right after my last post. I put it all back together and the pistons went right back to where they were.

So am I correct to assume that the natural resting position of the pistons is at the point where the pads are just BARELY touching the disk? Cuz that's where I'm at w either old or new pads.
Thanks again.

[Slingblade]

You are correct, sir. Very little travel on the pistons. The movement of the disc and the floating pins will create space while everything is turning, you know, when your ripping the snot out of it down some trail.. They don't always work perfectly while sitting still.

[Onetrackmind]

Awesome. I think I may actually be done with this brake then. Now...I can devote more time to the overflowing float bowl :-)

[Red Rider]

I'm not sure if it's the stock disk or not. It is measuring about 3mm thick though.

I put the old pads back on (which still had some life left in them) hoping that would solve the clearance issue and it looked good until I depressed the brake lever. The Pistons extended and did not fully retract. Also when I go to push the Pistons back in they move freely, but only one at a time. When I push one in, the other pops out the same distance.

Your disc appears to be OEM, and it's thickness is not an issue. The pistons will never fully retract. If they did, you wouldn't get instant braking when applying the brakes with worn pads. When you push in on one piston, the brake fluid will take the path of least resistance, and push the other piston out.

Based on your last post, it sounds like you have them working properly now, with no more dragging?

[Onetrackmind]

As far as I know, there is no dragging. It doesn't sound or feel like it when I turn the wheels by hand. I think I'm good, but won't really know until I ride it.

I'm trying to figure out why my carb is overflowing even with a new needle valve. Will try to adjust the float tang a little and see if that fixes it. Might be able to test ride this evening.

Thanks again for the input.