Check brake hoses and banjo bolts

Brake hoses carry fluid under high pressure from the master cylinder to the caliper. A banjo bolt is the hollow bolt with a round fitting that joins a hose to the master cylinder or caliper, sealed by a soft washer on each side. Old, cracked or swollen hoses can burst when you brake hard. This check finds leaks and damage before that happens.

Safety

• If any hose is cracked, swollen, rubbed through or leaking, do not ride. Replace the hose.
• Brake fluid damages paint and eyes. Wear glasses.

You need

• A torch and a clean rag. A wrench only if a banjo bolt needs tightening (see step 6).

Steps

1. Clean the hose fittings with a damp rag so you can see fresh leaks.
2. Follow each hose from the master cylinder to the caliper. On combined braking (CBS) bikes, also follow the hoses and rigid metal pipes to the CBS unit and to the front caliper (K-Light 125 has these).
3. Pull the lever and press the pedal hard several times while you watch the fittings. Look for wet spots or drips.
4. Bend and twist each rubber hose gently with your fingers, especially near the fittings and where it flexes when you steer or when the suspension moves. Look for: - fine cracks in the outer cover, - bulges (swelling) when the brake is applied, - rubbed or cut places where the hose touches the tyre, fork or frame.
5. Turn the handlebar full left and full right. The hose must not stretch, kink or catch.
6. Check the banjo bolts for wet fluid or crusty dried fluid round the washers. A weeping banjo usually needs new sealing washers, not more force. Tighten only to the model torque: K-Light 125: 30 N·m.
7. Check metal pipes for dents, rust and loose clips.

Check your work

• No wetness at any fitting after hard pulls on the lever and pedal.
• No cracks, bulges or rubbing.
• Hoses follow their original route and do not pull at full lock.

If it did not fix the problem

• A hose is damaged: it must be replaced and the system bled. Replacing a hose means opening the hydraulics; follow Replace brake fluid and bleed the brakes, or the workshop routine on a CBS or ABS bike (Check a combined braking system (CBS)).
• Leak at the lever: Check the brake master cylinder.
• Leak at a piston: Rebuild a brake caliper.

Reference values (K-Light 125)