My son (living away, I'm his consultant by phone) is having brake problems on his 2001 Sportsman 500. Machine has only 1,000 original miles, not ridden often, mostly for hunting, never been abused, etc. He was having trouble with the foot pedal rear brakes, brake line bad, and while doing the job, after removing most of the front half of the machine decided to go through the whole brake system. In short, new brake pads (aftermarket) New Seal Kit, clean everything. etc., All back together, VERY WEAK BRAKES, No evidence of fluid leaking, Vacuum bleed several times, still weak, set hand brake overnight, no help, clean and bleed foot pedal system, bleed brakes again, still weak, doing everything as he should, but he can turn front wheels by hand with hand brake set, oh, adjusted brake pad adjuster hex bolt as specified in manual. I can't see where he is missing something, but really no stopping power now. He is a decent wrencher but is stumped by this one. I think there is still air in lines, he says he can't see how. My advice at this point, keep bleeding, But any and all ideas will be appreciated. At this point, no idea will be considered crazy. Thank You--Lou

 

Did you replace the seal kit in the rear master cylinder also? They have these on ebay.Polaris Sportsman 400 500 600 700 800 Rear Foot Brake Master Cylinder Seal Kit | eBay
Kinda my advise too on continue to vacuum bleed if new pads installed and adjusted, main master cylinder kit replaced and no sign of leaks.Only thing left if it doesn't build up (which I don't advise often) is to clamp the main line coming from the master cylinder to see if the master cylinder is able to build up pressure in itself. Some times repair kits don't help and a new master cylinder may be needed.

 

So he now has weak brakes front and back now?

Just in case he did not know, the hand lever operates the front and rear brakes simultaneously (60% front 40% rear) the foot lever and master cylinder is really just a separate back up rear system in case of a main brake failure.
That's why the rear brake has two lines going to it.