Bleeding Tips:
When bleeding, keep these points in mind:
• It helps to "pre-fill" the calipers, master, and lines as you re-assemble the components after an overhaul.
• Move the lever (or pedal) deliberately…don't thrash. You're trying to move fresh fluid in a manner that displaces the fluid and air froth already in the system. If your action on the lever (or pedal) is too aggressive, you risk creating more froth in the system.
• When moving the lever (or pedal), stop about ½" short of max travel on each stroke.
• Put some grease on the bleed nipples to prevent air entry when the bleed nipples are cracked open (especially important when vacuum bleeding)
• Open the bleed nipple on each stroke just as you begin moving the lever (or pedal).
• Very important: open the bleed nipple just enough to let a very small amount of fluid pass through. If you open the bleed nipple too much, you will lose "feel" at the lever (or pedal) and you'll have a harder time stopping at the right moment on each stroke.
• Close the bleed nipple at the end of each stroke before you release the lever (or pedal).
• It's sometimes necessary to "burp" the banjo fittings to release trapped air.
• Judicious tapping with a suitable rubber mallet at suspected locations of trapped air is sometimes helpful in getting them to move.
• If you have a highly aerated (frothy) mixture in your system, sometimes it helps to put pressure on the fluid by squeezing the lever (or pedal) overnight. For the lever, I use a zip-tie and for the pedal, I use a 5 pound dumbbell hanging from the end of the pedal. This will firm up your lever by putting the air back into suspension with the brake fluid. Then, you will need to re-bleed again the next day to replace the air-contaminated fluid in the system. Otherwise, the lever firmness you gained overnight will soon be lost as the air falls back out of suspension again...trust me it will!
• DON'T MIX DIFFERENT TYPES OF BRAKE FLUID. GL1000s require DOT 3 brake fluid. I use Castrol brand brake DOT 3 fluid with great results. Brake fluid specs are confusing. For example, DOT 5.1 is marketed as "universal" brake fluid and is supposed to be compatible with DOT 3 and DOT 4. However, DOT 5 brake fluid is silicon-based and not compatible with any other type of brake fluid. Be safe and don't confuse the next owner of you bike or your mechanic. Always use DOT 3 brake fluid.
• Brake fluid is hydroscopic (attracts water). This has two implications. Over time, the water absorbed by brake fluid will effectively lower the boiling point of your fluid rendering it less effective under hard use. Secondly, the absorbed water wreaks havoc on calipers and brake pistons causing rust and pitting. If you don't change your brake fluid regularly, eventually your brakes will fail ...it's a certainty! I recommend that you change brake fluid ever 2 years religiously.
• Make sure the by-pass port in your master cylinder is open and clear. This port is the smaller of the 2 ports which allow fluid to travel from the reservoir into the cylinder. This small orifice is easily blocked by small amounts of crud. If this small port is blocked, you'll have all sorts of brake problems including difficulty bleeding the system. You must remove the reservoir to inspect and clean these very important ports.
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