How to Bleed and Replace Brake Fluid on a 2017 Polaris Sportsman 450 HO

Shop parts for a 2017 Polaris Sportsman 450 HO ATV.

This guide from MotoSport walks you through a professional, safe brake fluid change and bleed for a 2017 Polaris Sportsman 450 HO. Follow every step, use the right tools and fluid, and respect safety cautions — brake maintenance is critical to safe riding.

What you need

  • DOT 4 brake fluid (verify owner’s manual for your specific unit)
  • Clear plastic tubing that snugly fits the bleeder nipples
  • Clean collection bottle or jar, minimum 16 oz
  • Wrench set for bleeder nipples and banjo fittings (use correct size)
  • Turkey baster or fluid syringe (to remove old fluid from reservoir)
  • Clean shop rags, gloves, eye protection
  • Brake cleaner and a small brush
  • Optional: hand-held vacuum bleeder or pressure bleeder for one-person operation

Model-specific notes for the 2017 Polaris Sportsman 450 HO

  • The Sportsman 450 HO uses a single master-cylinder feeding front and rear calipers; confirm reservoir location on your machine before starting.
  • Polaris recommends DOT 4 brake fluid for many 450 models — always confirm with your owner's manual or the reservoir cap marking before topping up.
  • This model has exposed painted bodywork and plastics; brake fluid will damage paint and plastics quickly. Protect surrounding surfaces and immediately clean any spills.
  • The brake lines and fittings on the 2017 Sportsman are standard metric sizes. Keep replacement crush washers on hand if you open banjo fittings.

Preparation

  1. Park on level ground and secure the ATV with the ignition off. Remove the key.
  2. Remove the seat and any plastics necessary to access the brake master-cylinder reservoir and calipers. Clean the reservoir area to prevent contamination.
  3. Wear gloves and eye protection. Keep rags handy for spills.
  4. Open the reservoir cap and use a turkey baster or syringe to remove as much old fluid as possible without letting dirt enter the reservoir.
  5. Top the reservoir with fresh DOT 4 fluid to the fill line, then replace the cap loosely (do not tighten) to reduce air entry during bleeding.

Bleeding order & method

Use a furthest-to-nearest approach relative to the master cylinder to reduce air retention. On most Sportsman 450 HO layouts that means starting with the rear caliper(s) furthest from the master cylinder, then the front caliper(s). If your unit has independent left/right plumbing, bleed the wheel farthest from the master cylinder first. If unsure, visually trace the brake line from the reservoir to determine the sequence.

Two-person manual pump-and-bleed

  1. Have an assistant sit on the ATV to apply steady pressure to the brake lever/pedal. For pedal systems, they should apply moderate, steady pressure; for lever systems, a continuous firm squeeze works.
  2. Place a clear hose over the bleeder nipple of the furthest caliper and route it into a collection bottle partially filled with a little new fluid to prevent air from re-entering the hose.
  3. Loosen the bleeder nipple about a 1/4 to 1/2 turn. The assistant maintains pressure as fluid and air bubble exit into the bottle.
  4. When flow slows, tighten the nipple, then have the assistant release and reapply pressure. Repeat until no air bubbles appear and fluid runs clear.
  5. Check and top the master-cylinder reservoir after every cycle to keep it from running dry.
  6. Repeat the process for each caliper in the farthest-to-nearest order.
  7. After final caliper is bled, pump the lever/pedal to confirm firm, consistent pressure. Tighten all bleeder nipples to proper snugness and securely replace reservoir cap.

One-person vacuum or pressure bleeder method

  1. Attach the vacuum hose to the bleeder nipple and run the collection into a bottle. Apply vacuum and open the nipple; vacuum will draw fluid and air out.
  2. Advance through the same farthest-to-nearest order, monitoring reservoir level and topping as needed.
  3. If using a pressure bleeder on the reservoir, set low pressure and open each bleeder in turn until clear fluid exits and no air bubbles remain.

Flushing the system

To fully replace old fluid, pump fresh fluid through until the expelled fluid is the same color and clarity as new DOT 4. This usually requires multiple reservoir refills and bleeding cycles. Never reuse collected fluid.

Final checks

  • Clean all fittings and surrounding areas with brake cleaner; check for leaks at banjo bolts and bleeder nipples.
  • Properly torque any loosened banjo or mounting bolts per Polaris spec in your service manual (consult manual for exact values).
  • Confirm brake lever or pedal has firm resistance with no sponginess. If spongy, repeat bleeding until all air is removed.
  • Dispose of old brake fluid responsibly at a hazardous waste facility.
  • Test ride at low speed in a safe area to verify brake performance before regular use.

Common problems & troubleshooting

  • Persistent spongy lever: likely air still trapped. Re-bleed using vacuum or pressure method for best results.
  • Brake drag after bleeding: check caliper pistons and slider pins for corrosion or sticking; clean and service as needed.
  • Leaking fittings: replace crush washers on banjo bolts and ensure bleeder nipples are not damaged.
  • Contaminated system (old, dark or gummy fluid): perform multiple flush cycles until fluid is clear.

MotoSport maintenance tips

  • Keep a maintenance log with fluid change dates and mileage/hours; DOT fluid absorbs moisture with time, so replace on schedule rather than waiting for problems.
  • Always carry a small bottle of DOT 4 and basic bleed kit on long rides for emergency topping if you suspect contamination or leaks.
  • If you're not comfortable bleeding brakes or if the system shows leaks or stuck calipers, bring the ATV to a qualified technician to avoid safety risk.

Following these steps will ensure a clean, air-free brake system for your 2017 Polaris Sportsman 450 HO — helping maintain safe, reliable stopping power on every ride.

Related Shopping Categories

Shop Brake Fluid for a 2017 Polaris Sportsman 450 HO ATV.

Shop Brake Bleeders for a 2017 Polaris Sportsman 450 HO ATV.

Shop Brake Pads for a 2017 Polaris Sportsman 450 HO ATV.

Shop Brake Lines for a 2017 Polaris Sportsman 450 HO ATV.

Shop Brake Tools for a 2017 Polaris Sportsman 450 HO 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.