How to bleed and replace brake fluid on a 2012 Polaris Sportsman BIG BOSS 800 6X6

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This MotoSport guide walks you through safely draining, replacing, and bleeding the brake fluid on a 2012 Polaris Sportsman BIG BOSS 800 6X6. Follow these steps exactly to restore firm brake feel and maintain braking performance for towing, hauling, and work-duty use. Read all steps before starting. Work on a level surface, use personal protective equipment, and keep brake fluid away from paint and plastic.

What you'll need

  • DOT 4 brake fluid (use the fluid specified in your owner's manual if different)
  • Clear tubing that fits snugly over each bleeder nipple
  • Catch bottle for old fluid and a sealable disposal container
  • Wrenches for bleeder nipples (typically 8mm or 10mm)
  • Turkey baster or suction gun (for removing fluid from master cylinder)
  • Vacuum brake bleeder or a helper to pump-and-hold
  • Clean rags, gloves, and eye protection
  • Tile or drip pan to protect plastic and paint

Special notes for the 2012 Sportsman BIG BOSS 800 6X6

  • The 6X6 configuration increases load on rear brakes when towing; inspect pads, rotors, and lines for heat damage or leaks before bleeding.
  • This model does not typically have wheel ABS; bleeding is conventional but confirm by visual inspection of rear hub assemblies.
  • Master cylinder reservoir is mounted on the handlebar area; don't allow the reservoir to run dry during bleeding — drawing air into the system will require extra effort to purge.
  • If your machine has a parking brake/drum assembly on the rear, ensure the parking brake is released while bleeding those circuits so calipers operate freely.
  • Heavy use or towing warrants DOT 4 for higher boiling point; follow manufacturer guidance if different.

Preparation

  1. Park on a level surface, engage the parking brake, and turn off the engine. Chock wheels for safety.
  2. Clean the master cylinder cap area. Remove the cap and diaphragm carefully to avoid contamination.
  3. Use a turkey baster or suction gun to remove as much old fluid from the reservoir as possible. Wipe any residue from around the filler opening.
  4. Top up the reservoir with fresh DOT 4 fluid to the recommended level. Keep the new fluid sealed until needed.
  5. Locate the bleeder nipples on each caliper or wheel cylinder and remove dirt. Place a catch bottle under each nipple and push clear tubing over the nipple to route fluid into the bottle.

Determine bleed order

Because routing on the 6X6 can vary, pick the caliper furthest from the master cylinder first and finish with the closest. If unsure, visually trace the brake lines from the master cylinder to each caliper. Typical sequence: furthest rear caliper – other rear caliper(s) – front caliper(s) – master cylinder line closest to wheel.

Bleeding methods

Method A — Vacuum bleeder (recommended solo option)

  1. Attach vacuum pump tubing to the bleeder nipple and the other end to a clear catch bottle.
  2. Crack the bleeder nipple one-quarter to one-half turn. Apply vacuum and open the nipple until fluid flows clear and bubble-free. Close the nipple while maintaining vacuum, then stop vacuum and tighten nipple.
  3. Keep the master cylinder topped up between wheels to prevent air entry.
  4. Repeat for each caliper following the chosen sequence until only clean fluid appears and pedal feel is firm.

Method B — Pump-and-hold with a helper

  1. Helper pumps brake lever/pedal several times and holds firm pressure.
  2. You open the bleeder nipple briefly to allow fluid and air out into the tubing, then close the nipple while the lever/pedal is still held down. Repeat.
  3. After each cycle, allow the helper to release the pedal slowly and pump again. Keep the reservoir topped up at all times.
  4. Continue until clear, air-free fluid appears and pedal lever feels solid.

Method C — Reverse flushing (use with caution)

Rarely used and only when contamination or stubborn air pockets persist. If attempted, use a diagnostic reverse-bleed tool and follow strict procedure to avoid introducing more air or damage to seals. MotoSport recommends vacuum or pump-and-hold as first choices.

Finishing steps

  1. After the last caliper is bled, top the master cylinder to the proper level and replace the cap and diaphragm securely.
  2. Clean any spilled fluid from painted or plastic surfaces immediately with water and mild detergent — brake fluid can damage finishes.
  3. Test brake lever/pedal feel at low speed in a safe area. If spongy, repeat bleeding until firm. If sponginess persists, inspect for leaks or a failing master cylinder.
  4. Properly dispose of used brake fluid per local regulations; do not reuse or pour down drains.

Inspection & maintenance tips specific to the 6X6 Big Boss

  • Check brake lines for chafing where harnesses route across frame rails unique to the 6X6 layout.
  • Inspect caliper mounting bolts and pads for uneven wear caused by extra rear load; replace pads and hardware in matched sets when necessary.
  • Because this model may be used for heavy hauling, monitor rotor thickness and pad life more frequently than for standard ATV use.
  • Keep a maintenance log of fluid changes; flushing every two years or sooner under heavy-duty use prevents moisture buildup and boiling under load.

Troubleshooting

  • Persistent soft pedal after thorough bleeding: check for internal master cylinder leaks or collapsed hoses; replace suspect parts.
  • Visible leaks at calipers or hoses: replace seals or hoses before re-bleeding.
  • Brake drag after bleeding: ensure pistons slid freely and caliper guide pins are clean and lubricated with high-temp brake grease.

Following this MotoSport procedure will restore a firm brake pedal and reliable stopping power on your 2012 Polaris Sportsman BIG BOSS 800 6X6. When in doubt, consult a professional technician or your owner's manual for model-specific clarifications.

Related Shopping Categories

Shop Brake Fluid for a 2012 Polaris Sportsman BIG BOSS 800 6X6 ATV.

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Shop Brake Pads for a 2012 Polaris Sportsman BIG BOSS 800 6X6 ATV.

Shop Brake Lines for a 2012 Polaris Sportsman BIG BOSS 800 6X6 ATV.

Shop Brake Tools for a 2012 Polaris Sportsman BIG BOSS 800 6X6 ATV.

Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.