Plunger on my rear master cylinder was stuck in took it apart got everything free up now I only have good front brakes when the rear brake pedal is depressed and can't get the rear brakes to pump up and build any pressure bled front and rear numerous times. Have good fluid and no air coming out But still rear brake pedal goes right down. Is the master cylinder bad

 

Tiny rear master cylinders are bad about seals leaking and not building up pressure. Most people don't use the brake pedal and that's one of the causes. You can try blowing out the lines that go through the rear brake line splitter block and see if that helps.Plus a mityvac can possibly help. Can't find a rebuild kit for this dual line master master cylinder. Plus haven't found an after market one for it like you can for the single line set up. Expensive for what it is.http://www.ebay.com/itm/OEM-3-4-Dual....c100507.m3226

 

Wow, that's expensive.
I picked up one of them for $20, for a 700 twin, and it has performed great. Been on that bike for a year and a half now.

 

Yes the ones used on all the other machines used a single line master cylinder for the rear brake and you can find these cheap.This dual line master cylinder is only used on the ATP 330/500 and Sportsman X2 with the dual calipers and no one that I've found makes an after market one for it. First diagram is on the 2005 ATP with the dual calipers. The next one is on the same year model 700.