Bleeding 1990 Yamaha YSR50 Brakes at Home

Shop parts for a 1990 Yamaha YSR50 Motorcycle.

The 1990 Yamaha YSR50 uses a hydraulic disc brake at the front and a mechanical drum at the rear. The front disc is fed by a small master cylinder and reservoir on the right handlebar, and it’s the only part of the brake system that uses fluid. Bleeding this bike means bleeding the front brake only; the rear drum is adjusted, not bled.

Reasons to Refresh the Fluid

Brake fluid absorbs moisture over months and years. That water lowers the boiling point and encourages corrosion that can lead to a sticky piston and worn seals, especially on a bike that has been stored. Fresh fluid brings back a firm lever and protects the hardware.

  • Spongy lever feel or extra lever travel
  • Dark, cloudy fluid in the reservoir
  • A bike coming out of storage
  • Recent front brake work

Tools and Materials

  • Fresh brake fluid of the type marked on the master cylinder reservoir cap, from a sealed container
  • A box-end wrench that fits the bleeder valve
  • Clear tubing and a catch bottle
  • A small syringe
  • A screwdriver for the reservoir cap
  • Penetrating oil
  • Rags and water for cleanup

Getting the Bike Ready

Support the bike securely upright. Turn the handlebars until the reservoir is level. Cover the tank and bodywork with rags, since brake fluid can ruin paint and plastic. Clean spills immediately with water. Wipe the reservoir cap clean before opening, and soak a rusty bleeder with penetrating oil before loosening it.

How to Bleed the Front Brake

  1. Remove the reservoir cap and diaphragm.
  2. Remove most of the old fluid with the syringe, keeping some in the bottom so air can’t enter.
  3. Clean out residue and refill with fresh fluid.
  4. Connect the clear tube to the caliper bleeder, running the other end into the catch bottle.
  5. Squeeze and hold the lever.
  6. Open the bleeder about a quarter turn.
  7. Close the bleeder before releasing the lever.
  8. Repeat, topping off the reservoir every couple of strokes.
  9. When the fluid is clean and bubble-free, close the bleeder snugly.

The Rear Drum Brake

The rear brake is mechanical, linked to the foot pedal. There’s no fluid to change. Check the adjustment and wear indicator, and make sure the brake releases fully.

Pro Tips

  • Smooth, full strokes move fluid better than quick pumping.
  • Use a box-end wrench to avoid rounding the small bleeder.
  • Check the hose for cracks or swelling.
  • Discard collected fluid rather than reusing it.

After the Bleed

Fill the reservoir to the correct level, reinstall the diaphragm and cap, and clean the area. Check for leaks and dispose of the old fluid properly. The lever should feel firm and should not creep under steady pressure. Spin the front wheel to check for drag, and test both brakes at low speed in a safe area before riding.

Know When to Get Help

If the lever stays soft after repeated bleeding or the caliper or master cylinder leaks, the seals are probably worn. A rebuild or replacement may be needed, and a shop can help.

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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.