So I have replaced the rear caliper and pads, and rear master cylinder on it. I now finally have back brakes. The rear master though will not engage, even though I have bled it multiple times. It just feels like nothing when you press down. Really not a big deal since I don't use it. The big problem is when I use the hand brake I have to pump it at least once before I use it every time if I go a couple minutes with out using it. It is not leaking fluid anywhere, and I have bled them (almost a whole bottle of brake fluid). No air comes out from the front or the back. Any thoughts?

 

May be as simple as the rear caliper halves small o-rings seeping air. This can cause the problems you're having.Might be time to replace them. They come with the piston kit.Polaris Scrambler TrailBlazer Trail Boss Rear Brake Caliper Seal Rebuild Kit 123

 

Shoot I hope not. It is a brand new caliper. Would it leak fluid if that was the cause. There is no fluid leak at all.

 

Sorry,missed the part on the new rear caliper and the rear master cylinder Also I'd use a mity vac bleeder starting at the rear caliper,then right front ,then left front.You may have trapped air in the lines causing problems.If this doesn't help then the main master cylinder piston and seals may be sucking in air. It's a pity they don't offer rebuild kits for this model like they did on previous models. Polaris ATV Parts 2004 A04BG50AA SCRAMBLER 500 4X4 CONTROLS-MASTER CYLINDER-BRAKE LINE Diagram Guess they're making aftermarket master cylinders cheaper than rebuilding one even if Polaris had the rebuild kit.http://www.ebay.com/itm/Front-Left-B...BYU1eK&vxp=mtr