Front Disc Brake Release

[WS/CC]

Hi Everyone,

I'm tidying up an '81 GS 450 to get it back on the road after many years in storage, and was hoping I could find some help troubleshooting the front disc.

After bleeding the lines and adjusting everything, the caliper piston won't return when the lever is released - the end result is the the pads will seize onto the disc after 5 or 6 pulls of the lever.

The piston moves freely when the caliper is off the bike, and as far as I can see there are no leaks in the system and it's all bled properly.

I'm a little unclear on how the piston normally moves back into the caliper. Is it simply a hydraulic action as the lever is released back to the open position? If so, would an air leak defeat this action? There's no spring return or similar mechanism anywhere that I can see on the bike or in the manuals.

Thanks for any help with what I guess is a very basic concept/question - I'd just like to get an idea of what to look for before I go buying up parts and replacing everything.

Cheers, Hamish.

[tkent02]

Check for a blocked return port in the master cylinder. It's tiny, and if it's blocked there is no way for the fluid to leave the caliper, so the brake can't release.

[Agemax]

clean the pins and the areas of the calipers where the pads slide on. apply a smear of copper grease too. if they are binding the pads wont release

[oldrookie]

Maybe we should swap some parts. Between our two bikes we might get the brakes to work properly. Mine won't retain pressure, yours won't release.