Rear brake problem

[moloprintz]

We're on our way home Saturday after a low speed curvy ride.
I tend to use my rear brake for control in the curves.
If I have the proper RPM and I've still got too much energy going in I'll use the rear brake.
Late in the afternoon I applied rear brake and the pedal went all the way down with no effect.
No problem, light front brake with engine braking and everything’s nice and smooth.
I tried the brake pedal a couple of times with the same result each time.
After a refuel and rest stop the rear brake works fine.
Sounds like a master cylinder problem.
The question is do I buy new, low mileage used or a rebuild kit?
If a rebuild kit, do I need to hone the cylinder wall?
Has anybody else had this problem?

Mike