After my Wr450 sat for five months waiting for the snow to melt. I took the motorcycle out for a ride. I had no rear brakes. After riding 60 miles or so with no rear brakes I took the Yamaha home and tried to bleed the rear master cylinder. No such luck it with not pump up at all. My question is seeing how a new rear master cylinder is about 100 dollars and the rebuilt kit is about 20 dollars is it worth trying to rebuilt the master cylinder?