Overflowing master cylinder

What would cause the master cylinder reservoir to overflow and weep on the brembo version on my Ktm 690? The pads are not dragging on the disk and the fluid isn't boiling or even getting warm. Have emptied out a few mls of fluid a few times but last 2 rides I have had the lever play reduced to nil and fluid start to weep.

Damaged bladder under the lid?

Possibly, but the reservoir is definitely "producing" fluid. I.e. I empty a bit out and after the next ride it is full again. One other symotom is the lever action becomes engaged with the smallest pull of the lever.

Have you installed new pads recently ? They could be thicker than the previous ones causing this condition.

Its not possible for the reservoir to "produce" fluid.

bent rotor forcing pads open and backflowing fluid?

x2 no "production" happening

Thanks for that, I'm glad you think it is strange also. It defies logic.

No new pads. They are originals, about 70% spent. Also the rotor is true and balanced. That's why I'm stumped.

Does your lever feel solid and not spongy? Air in the system will expand more than fluid when things warm up from use. Does the brake completely release when warmed up?
Just a thought.

Not spongy at all, nice and firm, good feel and stopping power.

Weird,
I'm grasping at straws here but, the wheel bearings aren't loose are they?

Na, they are in excellent condition. I removed fluid down to the min level and went for a long ride today with a plus 1 on the back and didn't see any escape. I'll see how it goes. Maybe I can start selling the excess.

Just bleed off a tad more. Common error is to over fill the cylinder