If the fluid in the clutch master cylinder reservoir is dark, or the clutch lever feels soft and spongy when pulled in, it may be time to bleed (or replace) your clutch system. Flushing and bleeding the system will prevent bad fluid from wreaking havoc within your clutch master cylinder, and will ensure a firm, positive clutch engagement. The task requires only a few small tools and is much easier to do than it seems.
Locate your clutch slave cylinder fluid fitting and attach your plastic hose and fitting. Be sure that the hose is long enough to reach your overflow bucket.
Open your clutch master cylinder cap and remove the diaphragm.
Suck out any fluid in the reservoir using a syringe. This step is optional, but prevents contaminated fluid from entering the clutch line.
Fill the fluid reservoir and lightly tap the line, lever and reservoir to free any air bubbles trapped in the fluid. Keep the fluid reservoir filled to prevent air from entering the line.
Pump the clutch lever three to four times, then hold it in.
Open the fluid fitting on the slave cylinder a half turn. A small amount of clutch fluid should appear in the hose.
Close the fitting before the fluid stops moving and release the clutch lever.
Repeat Steps 2 to 4 until the fluid's colour is consistent and without air bubbles. Fill the fluid reservoir as needed.
Test the clutch master cylinder by putting the bike in gear with the engine off. The clutch should disengage and let the bike roll. Re-check the fluid fitting to ensure that it is closed tightly to prevent air from entering the system.
Brake fluid is caustic and will damage painted parts, so cover any exposed bodywork or painted areas. Wipe up spilt brake fluid immediately and rinse heavily with water. Be sure to use the proper DOT rated brake fluid for your motorcycle. Refer to your Owner's manual for details. Please dispose of your old brake fluid properly. Most auto parts stores accept used brake fluids for recycling.