Brake Problem Twincam RT

[Our Gee]

Hi all,
half way through my usual winter brake service on our R1200RT Twincam and a new problem has arisen. After a thorough clean of the front off side caliper pistons I am unable to retract the pistons back into the caliper to re-fit the pads. Individually, each piston will fully retract into it's respective position. It's when I attempt to retract all four together everything just becomes solid and won't budge. I have done this job many times before and never had a problem. Any advice appreciated,
Thanks.

 

[fatnfast]

Is the brake fluid overfilled? Maybe when you push all four in at once the level in the reservoir completely fills to the lid. Nowhere for the fluid to go so no more piston retraction.

 

[Posh Pete]

Is the brake fluid overfilled? Maybe when you push all four in at once the level in the reservoir completely fills to the lid. Nowhere for the fluid to go so no more piston retraction.

My thoughts also. Did you remove the reservoir cover. Compressing the air in the reservoir will also stop the pistons.

 

[sparky56]

Slacken the bleed nipple, it should push back then. just watch out for the squirt of fluid as you push them back.

 

[Our Gee]

Reservoir cover was removed and level just above Min. It did feel like a "hydraulic lock" so as Sparky suggested I slackened the bleed nipple a touch and pistons pushed back ok. Still confused though as to why this should happen, never happened before.
Thanks for the suggestions.

 

[ahutcheon]

Rubber brake hose collapsed internally? Master cylinder piston not returning fully? Just trying to think of things that would stop fluid getting back up to the reservoir.

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