How to Bleed Brakes on a Chinese 150CC ATV

Most Chinese ATVs rely on a pair of brake drums behind both front wheels and a single disc brake along the rear axle. On some models, the front drum brakes are substituted with disc brakes for increased stopping power. Hydraulic brakes are prone to air and water infiltration that reduces braking effectiveness. This is often perceived as a soft feeling at the brake lever or pedal, as well as an increase in the effort required to stop. Removing air and water from the brake circuit, or bleeding, is accomplished through a set of nozzles built into the brake calipers.

Things You'll Need

• Socket set
• Breaker bar
• Jack
• Phillips screwdriver
• Hand pump
• DOT 3 or 4 brake fluid
• Box-end wrench set
• Three feet, 1/4-inch inner diameter vinyl tubing
• Shop towel
• Torque wrench

Instructions

Front Disc Brake Bleeding Procedure

1. Park the ATV over a level work surface. Loosen both front wheel lug nuts using a socket and a breaker bar. Lift the front wheels off of the ground using a jack. Remove the lug nuts and both front wheels.

2. Remove the fluid reservoir lid from the front brake master cylinder on the right handlebar using a Phillips screwdriver. Pull the rubber diaphragm out of the reservoir. Suck out most of the brake fluid from the reservoir using a hand pump. Leave at least 1/8-inch of fluid in the reservoir to prevent air from entering the brake circuit.

3. Fill the reservoir three-quarters full with DOT 3 or 4 brake fluid.

4. Pull the rubber cap off of the left front brake caliper bleed valve, located at the top of the caliper. Slip a box-end wrench over the hexagonal portion of the valve, then push a three-foot long piece of 1/4-inch inner diameter clear vinyl tubing over the valve. Place the opposite end of the tubing into a resealable plastic container.

5. Turn the bleed valve counterclockwise a quarter turn, using the wrench, to open the valve. Pull in the brake lever slowly to push a small amount of air and brake fluid out of the bleed valve and into the tubing. Turn the valve clockwise to close the valve, then slowly release the brake lever to draw fresh fluid into the brake circuit. Repeat four to five times, then refill the reservoir.

6. Inspect the brake fluid trapped in the tubing. Ideally, the fluid will be light amber and should not contain air bubbles or debris. Continue to bleed the brake circuit if the brake fluid appears dark or is filled with air bubbles or debris.

7. Tighten the bleed valve against the caliper once the brake fluid in the tubing is clean and free of bubbles. Pull the tubing off of the bleed valve, using a shop towel, then push the rubber cap into place.

8. Remove the rubber cap from the right front brake caliper bleed valve. Place your wrench and the tubing over the bleed valve. Bleed the right brake caliper until the brake fluid is clean and free of bubbles. Tighten the bleed valve and push the rubber cap into place.

9. Refill the reservoir with brake fluid, then push the rubber diaphragm into place. Pump the brake lever several times. The lever should feel firm once it passes halfway through its range of motion, well before it reaches the right hand grip. Re-bleed both calipers if the brake lever feels soft or if it can be pulled completely to the hand grip. Reinstall the reservoir lid if the lever feels firm.

10. Mount both front wheels onto the ATV, then screw the lug nuts into place by hand. Lower the ATV to the ground, then tighten the lug nuts to 56 foot-pounds using a torque wrench.

Rear Disc Brake Bleeding Procedure

1. Follow the brake hose from the rear brake caliper, located on the right side of the rear swingarm, to the rear brake master cylinder near the right rear fender. Remove the cap from the master cylinder fluid reservoir, either by unscrewing it by hand or using a Phillips screwdriver. Pull the rubber diaphragm out of the reservoir.

2. Suck out most of the brake fluid from the reservoir using a hand pump. Leave at least 1/8-inch of fluid in the reservoir to prevent air from entering the brake circuit. Refill the reservoir three-quarters full with DOT 3 or 4 brake fluid.

3. Pull the rubber cap off of the bleed valve at the top of the rear brake caliper. Slip a box-end wrench over the hexagonal portion of the valve, then push a three-foot long piece of 1/4-inch inner diameter clear vinyl tubing over the valve. Place the opposite end of the tubing into a resealable plastic container.

4. Turn the bleed valve counterclockwise a quarter of a turn using the wrench to open the valve. Push down slowly on the rear brake pedal to push a small amount of air and brake fluid out of the bleed valve and into the tubing. Turn the valve clockwise to close the valve, then slowly release the brake pedal to draw fresh fluid into the brake circuit. Repeat four to five times, then refill the reservoir.

5. Inspect the brake fluid trapped in the tubing. Ideally, the fluid will be light amber and should not contain air bubbles or debris. Continue to bleed the brake circuit if the brake fluid appears dark or is filled with air bubbles or debris.

6. Tighten the bleed valve against the caliper once the brake fluid in the tubing is clean and free of bubbles. Pull the tubing off of the bleed valve using a shop towel, then push the rubber cap into place.

7. Refill the reservoir with brake fluid, then push the rubber diaphragm into place. Pump the brake pedal several times. The pedal should feel progressively firmer as it moves through its range of motion. Re-bleed the rear brake caliper if the brake pedal feels soft throughout its range of motion. Reinstall the reservoir lid if the pedal feels firm.

Tips & Warnings

• A hand-held vacuum bleeder, available from most auto parts stores, will make the job much easier. The pump operates by pulling brake fluid through the brake circuit by vacuum, eliminating the need to open and close the bleed valve.

• Brake fluid is a caustic solvent that will cause serious eye and skin irritation upon contact. Always wear protective gloves and glasses to avoid injury.

References

• Roketa RTX-250 Owner's Manual; Roketa Powersports/Nanjing Research & Development
• The Professional Motorcycle Repair Program: Brakes, Wheel Assemblies and Tires, Volume 22; Professional Career Development Institute