rear brake is gone?? master cylinder?

[damz]

for a while my rear brake has been getting less and less useful so been using fronts almost all the time, well anyway i noticed a dark brown stain on my pipes running past the right foot peg, paid no attention to it as the bike was filthy.

well anyway i took the rear calliper off to give it a good clean and check the brake pads to see if they were warn, everything was good but i stupidly pressed the brake pedal and one of the pistons popped off and some brake fluid poured out so thought fuck. well put everything back together and bled the system and put new brake fluid in the system.

however i have no feedback whatsoever from pressing the pedal, and after i had cleaned the pipes i noticed there was a dark brown liquid on it again so im guessing it must be the master cylinder or what ever its called.

am i correct in my assumption? if it is the cause of the problem is it difficult to replace? and would the parts be generic parts or will i have to order it from david silvers?

any ideas on what other problems could possibly be? doubt its a piston seal due to the leak being located next to the foot pedal and no leak noticed from the calliper while bleeding the system.

any help be much appreciated

(also any poor spelling is because i am totally shitfaced)
____________________
Current Bikes RVF400 - 94
Cars: RX7 FD, Eunos Roadster
Former Bikes: FZR 250R 89, ZX7R 98

[Finglonga]