Brake fluid is hygroscopic and attacks paint. Work cleanly, protect the bike and never let the reservoir run dry. If the system has ABS or combined braking, follow the service information.
Prepare and protect
Cover painted surfaces and use the correct fluid. Check the reservoir level and the bleed nipple. A helper makes the job easier, but a one-way bleed bottle works too.
Do not mix fluid types. Use the grade specified on the reservoir cap or in the manual.
Bleed in the right order
Start with the caliper furthest from the master cylinder if the system has multiple calipers. Pump, hold, open the nipple, close, release. Repeat until no air appears.
Keep the reservoir topped up. If it runs dry, you introduce more air and start again.
Deal with ABS and combined systems
Some ABS units need a diagnostic tool to cycle the pump. Combined systems may have multiple circuits. Follow the service information rather than a generic video.
If the lever is still spongy, check for a trapped air pocket at the master cylinder or a failing hose.
Test and dispose
Test the lever feel and the brakes at walking speed, then at normal road speed in a safe area. Clean up spilled fluid and dispose of it properly.
If the lever sinks under pressure, do not ride. Find the leak or the air.
Checklist
- Correct fluid type and fresh container.
- Painted surfaces protected.
- Reservoir kept above the minimum.
- Bleed sequence and nipple condition.
- ABS or combined-system procedure.
- Lever feel and leak check.
- Road test at low speed first.
Questions
Can I bleed brakes alone?
Yes, with a one-way bleed bottle or a vacuum bleeder. A helper is easier but not essential.
Why is the lever still spongy after bleeding?
Air may be trapped at the master cylinder, a hose may be expanding, or the master cylinder may be worn. Investigate rather than repeating the same bleed.
How often should brake fluid be changed?
Follow the manual. Fluid absorbs moisture even when the bike is used lightly, and humid climates shorten its life.
