[bikeguy57]

The front caliper on my CB360 builds pressure after repeated use. After several miles, the wheel is very hard to turn. If i crack open the bleeder screw, a small amount of fluid seeps out and the caliper releases. I have rebuilt the master cylinder and gone thru the rest of the system and can't find any obvious problems. Any help would be appreciated.

 

[Bird76Mojo]

The caliper likely needs taken apart, cleaned and brushed (little rubber ring groove with a pick), and a new seal installed. The piston may be ruined as well. The factory chrome plating on the piston swells after it starts to rust and makes the piston stick sometimes. New stainless pistons can be bought on Ebay and other places have new plastic ones as well. While you're at it, it'll be a good time to de-glaze the pads and rotor. Just make sure you do that on an ultra flat surface.



GB :mrgreen:

 

[jayel]

you also need to clean the old fluid and gunk out of the master cylinder, if it's partially plugged it won't allow the caliper to retract properly

 

[Bird76Mojo]

Jayel, he did mention that he rebuilt the master already.. Just pointing that out to eliminate further discussion or troubleshooting with it..

No offense mang

I forgot to add that he may have a rubber brake line that is too old, and collapsing in on itself. Thereby holding pressure on the caliper..

GB :mrgreen:

 

[66Sprint]

Just thought I'd mention that I have seen "rebuilt" masters that the return pinhole was still plugged on...............

 

[KERRY]

I've had that problem - I solved it by boring the fluid port in the master slightly larger. the problem seems to have been caused by the replacement cup having a slightly longer skirt than the original and it wasn't retracting far enough to uncover the forward port (from reservoir into the cylinder), so fluid in the master cylinder could not return to the reservoir when the piston was retracted as far as it could go. Corrosion in the wheel cylinder can cause the same brake drag symptom, that the piston doesn't retract - but releasing some fluid wouldn't get the piston to retract. (boy, can they get crusty - change the fluid every year or so, and take the wheel cylinder off and turn it upside down to do it. The crap - and water settles to the bottom). If you want some details on wheel cylinder rebuild, I have a file somewhere - ask about it.