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I’m pulling my hair out with this one. I have a 2017 sportsman xp highlifter. I replaced the front pads and the left front caliper, caliper was replaced because one of the outer tangs was broke off. Prior to this work both my hand brake and foot brake worked perfect. I gravity, power, and vacuum bled the system but I have no handbrake (goes almost to the handlebar before it does anything) but my foot brake works perfect. I replaced the hand master cylinder with no change and bleeding with all three methods. I tore off plastics to figure out my routing. My hand master drops to a distribution block that has four ports. Two ports go to my front calipers. The other port goes to my foot brake master cylinder/proportioning valve. I found a bleeder screw on my foot master cylinder, I bled that, got lots of air but still no change. After the foot master cylinder a line goes to another distribution block with two lines coming out going to each of my rear calipers. No fluid is leaking, all calipers are moving on their pins like they are supposed to. I cannot find info or understand how the proportioning valve works. Is it possible that it is only supposed to all a small amount of fluid pressure from the hand master travel to the rear calipers and that seal or spring has failed and when I pull the hand brake to much fluid is traveling to the rear causing this issue?
 

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I called it a proportioning valve because there seems to be some some application of the rear brakes when applying the front brake, at the very least I get fluid out the rear calipers when power bleeding them using the hand brake. Your diagram is correct in my routing of brake lines and components. I’m wondering if the foot master cylinder is allowing to much fluid to the rear brake lines when applying the hand brake?


Here's the brake system diagram - there is no proportioning valve unless you have the international model
View attachment 137458
r
 

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I believe (don't know for a fact) that applying the rear brake with the foot pedal eliminates the action of the hand lever applying the rear brake.

The one thing you have not tried is reverse bleeding.

Here's how I do it: Since air wants to rise in the system and tries to get back to the MC; I first get all 4 wheels off the ground with the front 6 to 10 inches higher than the rear - I remove one caliper, remove the brake pads and pump the piston out at least an inch - I install a c-clamp to hold the piston in position and place the caliper at it's lowest point (just let it dangle by the hose) - I then do the same to the other caliper (assuring the MC never goes dry) - I leave things alone for about a half hour - when I return, I cover the MC reservoir with a shop towel and starting with the caliper with the most line between it and the MC, I position the caliper so the line is at the apex and tighten the c-clamp slowly to depress the caliper piston back into the caliper body - when the piston is fully depressed, I do the same with the other caliper - I operate the lever to see if they feel better, then proceed to do the same with the front calipers - once all four calipers are fully depressed with the c-clamps still in place, I operate the lever to get a feel - if they feel tight, I'm done - if not, I repeat the process one caliper at a time starting with the one farthest from the MC until I get a tight lever - once I'm satisfied with the lever feel, I install the brake pads and calipers and gently, slowly pump up the system so the brake pads are in contact with the rotors - I pump slowly and gently to allow any air in the system to rise within the lines back to the MC without forcing the air into pockets and joints where it is hard to purge the air from - with the calipers all pressing the pads into the rotors, I tie the lever back keeping pressure on the system and crack each fitting, line joint and bleeder starting at the one farthest from the MC - pressurization of the system may need to be repeated as pressure and fluid are lost with each bleed. The last fitting/bleeder cracked is the line fitting at the MC. After all this, the brakes should be stellar. To finish, I check and bleed the foot brake if necessary.

It's my way - it works for me - hopefully it might work for you too. Just be sure to keep brake fluid covering the holes in the floor of the MC or you might have to start over. I have had to repeat the process to get good brakes, but I never fail to get the brake feel I expect or desire. On my CRF, the front brake was so good, I purposely introduced a small amount of air to soften the brake slightly. It can be locked with two fingers now - previously it only required one finger to lock the front wheel.

Good luck
 

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try bleeding from the farthest calipers to the nearest, that should get all the air out, brakes may be spongy till ridden for a while.
 

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This is kinda off topic.. but kinda related. Ever since getting my Polaris' I've wanted to separate the front brakes from the rear brakes. I've heard people say it can't be done. But never had a satisfactory explanation why not. In my (simple) mind you could just remove the line between the two and be done. Any input?

Would also be easier to bleed.. the OPs issue sounds like a bleeding issue to me. Bleeding brakes (and hydro clutches) can really be a pain sometimes.
 
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