How to Bleed and Replace Brake Fluid on a 2007 Polaris Sportsman 90

Shop parts for a 2007 Polaris SPORTS90 ATV.

This proprietary MotoSport guide walks you step-by-step through safely flushing old brake fluid and bleeding the brakes on a 2007 Polaris Sportsman 90 (MMY Polaris;SPORTS90;2007). Follow every step carefully & keep the work area clean to avoid contamination. Use only clean containers, new lines or syringes, and the correct DOT-spec fluid indicated in your owner's manual (DOT 3 or DOT 4 compatible fluids are commonly used — check your manual).

What you'll need

  • Correct DOT brake fluid as specified for your Sportsman 90
  • Clear plastic tubing that fits snugly over bleed nipples
  • Small clear catch bottle or jar
  • Wrenches sized for the bleed nipples (usually 8mm or 10mm)
  • Rubber gloves, shop rags, brake cleaner
  • Turkey baster or fluid transfer syringe (for reservoir removal)
  • Jack or ramps and blocks to secure the ATV if wheel removal is needed
  • Zip ties or clamps to keep tubing on nipples

Model-specific notes for the 2007 Sportsman 90

  • The Sportsman 90 uses a simple hydraulic brake circuit with a small master cylinder reservoir located near the handlebars. The reservoir cap has a diaphragm and filter that should be inspected for hardening or damage when servicing.
  • This model typically has drum or small hydraulic disc brakes front/rear depending on variant. Locate the bleed nipple on the caliper or wheel cylinder before starting so you know access and wrench size.
  • There is no ABS or complex electronic brake module on this youth ATV — bleeding is mechanical and straightforward, but the small reservoir means you must prevent air from entering the system.
  • Inspect brake lines for age-related cracks, chafing, or dry rot while servicing. Replace any suspect hoses to ensure reliable braking.

Safety first

  • Work on a level surface with the engine off and ignition key removed.
  • Wear safety glasses & gloves. Brake fluid damages painted surfaces — cover any paint and clean spills immediately with brake cleaner and water.
  • Never reuse old brake fluid or mix different fluid types.

Step-by-step fluid replacement & bleeding

1. Preparation

  1. Park the ATV level and secure it with the parking brake applied (if applicable). Lift or support the ATV if you need better access to wheels; ensure it is stable.
  2. Clean around the master cylinder cap and bleed nipples to prevent dirt ingress. Remove the reservoir cap and rubber diaphragm.
  3. Use a turkey baster or syringe to remove most old fluid from the reservoir. Do not let the reservoir run dry; leave a small amount so air cannot be drawn back in during initial operations.
  4. Top the reservoir with fresh brake fluid until near the maximum level mark.

2. Decide on bleeding method

Use one of these proven methods based on tools and helpers available:

Two-person method (fastest — recommended)
  1. Have an assistant slowly squeeze the brake lever/pedal several times and hold it compressed.
  2. Open the bleed nipple about a quarter turn. Attach clear tubing from the nipple to a catch bottle partially filled with old fluid to prevent air draw-back.
  3. Fluid and bubbles will flow into the bottle. Close the nipple before your assistant releases the lever/pedal.
  4. Repeat: have assistant pump and hold, open nipple, allow flow, close nipple, and top the master cylinder after each cycle.
  5. Continue until the fluid runs clear and bubble-free from the tubing, and the master cylinder is topped to the proper level.
One-person method with syringe or vacuum pump
  1. Fill the master cylinder to proper level.
  2. Attach clear tubing to the bleed nipple and the other end to a syringe or vacuum pump set to draw fluid slowly.
  3. Open the nipple and draw fluid until clear. Keep the reservoir topped during the process.
  4. Close the nipple before stopping the pump to prevent air entering the system.
Gravity bleeding (slow but simple)
  1. With the master cylinder full, open the bleed nipple and let gravity drain fluid into a bottle. This can take a long time and is less effective at removing trapped air.
  2. Keep the reservoir topped throughout.

3. Sequence

Bleed in the order that prevents air from trapping. For single-circuit small ATVs, bleed the farthest wheel from the master cylinder first, then the next farthest, finishing with the closest. If uncertain, bleed rear wheel(s) first then front.

4. Final checks

  • After bleeding all points, ensure all bleed nipples are snug but do not overtighten. Wipe away any spilled fluid.
  • Replace the reservoir diaphragm and cap. Clean tools and dispose of old fluid properly.
  • Test brake lever/pedal feel with engine off; it should be firm and not sink. If soft or spongy, repeat bleeding until firm.
  • Take the ATV for a low-speed functional test in a safe area to confirm braking performance before riding normally.

Maintenance tips & troubleshooting

  • Change brake fluid every 1-2 years or sooner if it appears dark or contaminated. Brake fluid absorbs moisture over time, reducing performance and increasing corrosion risk.
  • If the brake lever still feels spongy after bleeding, check for a collapsed master cylinder seal, leaking lines, or internal caliper issues. Replace worn seals or hoses as needed.
  • Keep a small spare bottle of the correct DOT fluid in your shop for top-ups during future maintenance.
  • If paint or plastic surfaces are exposed to fluid, rinse immediately with water and clean to avoid damage.

Parts & supplies note

When replacing hoses, seals, or caliper parts, use OEM-equivalent components sized for the Sportsman 90 to maintain braking reliability and safety. Refer to parts specific to the 2007 Sportsman 90 when ordering replacement components.

Closing

Bleeding and replacing brake fluid on a 2007 Polaris Sportsman 90 is straightforward when done methodically: keep the reservoir topped, avoid contamination, and follow a correct bleed sequence. If you encounter persistent issues or suspect internal component failure, consult a trained technician or schedule service with a trusted shop.

Related Shopping Categories

Shop Brake Fluid for a 2007 Polaris SPORTS90 ATV.

Shop Brake Bleeders for a 2007 Polaris SPORTS90 ATV.

Shop Brake Pads for a 2007 Polaris SPORTS90 ATV.

Shop Brake Lines for a 2007 Polaris SPORTS90 ATV.

Shop Brake Tools for a 2007 Polaris SPORTS90 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.