Slow build 71 Scamp 440

You don't have to have fluid loss for the master cylinder to be bad...it could be bypassing internally...fluid pushes past the O-rings when pressure is applied. It's cheap to buy the parts if your local place has them, but to guarantee they'll stay good, you need to hone the length of the cylinder. For my own piece of mind, it's easier to just buy a new or reman'd master cylinder and go from there...besides, if you want to paint it, it's easier to paint one without rust on it.