Most motorcycles use cables to connect the twist grip to the carb(s) or throttle bodies; many also use cables for the clutch, cold-start control, and even brakes. Servicing these critical components is fairly simple and prevents problems later. Maintenance intervals vary, and bikes ridden in dust, sand, or mud need extra maintenance. It’s good to at least perform a thorough control service annually; check the owner’s manual for recommendations.
Servicing Cables
Lubricating the inner cable allows it to slide easily, extending cable life and reducing control effort. If the bike is fairly new, you can just remove the cables from the controls and lubricate them while still in place on the bike. Several companies, including Motion Pro, Trackside, and Protect All, offer handy cable-lube tools and spray lubricants that make it easy to lube cables without removing them. Inject cable lubricant into the upper end of the cable until lubricant appears at the lower end of the housing. Use rags to protect the bike from drips.
If it’s been awhile since the cables were serviced, remove them for inspection. Refer to the service manual for model-specific procedures. Carefully note how each cable is routed in relation to others, and only remove and replace one at a time.
Clean and inspect the cables for wear, kinks, or damage; chafed covering and frayed cables; or loose pivot balls at the ends. Manually move the inner cable back and forth to check for binding. If the plastic covering is worn down so the coil winding is exposed, or if one of the fittings is damaged or worn, replace the cable.
Most bikes have two throttle cables; one pulls the throttle open, and the other pulls it shut as a safety measure (in case it sticks or a return spring fails). It’s crucial these be serviced and adjusted carefully. If you don’t have the proper tools, skills, or knowledge, take it to a professional.
Clean and lube pivot points, such as the clutch cable “barrel” in the clutch lever and the throttle cable barrels in the throttle housing. Lubricate sparingly with grease to prevent binding (which causes the cable to twist at the end and fail).
Most replacement cables are sold with little or no lubrication, so make sure they are properly lubricated before installing. While you are lubing the cables, remove the clutch lever and grease the pivot so it will operate smoothly and not wear out prematurely. Do this for the brake lever too, even if it isn’t connected to a cable. Make sure you reinstall the levers correctly. Cables must be routed carefully. Most shop manuals provide routing diagrams; be sure to follow these, and ensure the cables don’t get pinched when the steering is turned to full lock.
Slack or “Free Play”
Slack, or “free play,” of the inner cable is critical to the proper and safe function of your motorcycle. First adjust the outer cable adjustment sleeve, then adjust the inner cable. A lack of free play can cause the clutch to partially release and slip, which will burn it out quickly. If it is too loose, shifting can be difficult. Lack of free play in the brakes can cause drag, overheating, and failure. Generally, the levers should have enough free play to fit a dime in the gap when the lever is released. Service or owner’s manuals have cable adjustment procedures and free play specs. Release the locknut, adjust the threaded sleeve, and tighten the locknut.
Hydraulic Systems
Most motorcycles have the front brake lever connected to a hydraulic master cylinder. Many bikes also use hydraulic clutch actuation, with a master cylinder connected to, and pumped by, the clutch lever. These systems are normally self-adjusting but do need occasional inspection, fluid replacement, bleeding, and lever-pivot lubrication.
Fluid should be changed every two years. If your bike has ABS, refer to the shop manual before proceeding. Suction old fluid from the master cylinder reservoir. Refill with fresh brake/clutch fluid of a type recommended in the owner’s manual, typically DOT type 3 or 4.
Bleed the brake system at the caliper(s) and the clutch system at the clutch slave cylinder. Open the bleeder valve, using a small hose over the fitting to direct fluid into a catch bottle. Squeeze the lever, open the bleeder screw, and allow air and fluid to escape. Close the bleeder screw and release the lever. Repeat this until fresh clean fluid comes out steadily with no more air bubbles. Tighten the bleeder screw, refill the reservoir, and install the cap.
Before riding, test for proper operation of all controls. Operate front and rear brakes while stationary. With the engine idling in neutral, turn the handlebar from full left to full right and operate the throttle to check for cable binding.
By Ken Freund
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Advgrrl Motorcycle Adventures & More 
Some cables, like the stock throttle, cold start and clutch cables on my airhead, have an inner teflon sleeve and the factory recommends that no lubricant be used on the cable as it gums them up and could cause them to stick. They do recommend greasing the barrel where the cable attaches to the levers to allow the barrel to rotate smoothly. Also a little bit of oil on any exposed cable could prevent rust. I have been using teflon sleeved cables on my bicycle for thirty years and have never had them stick or rust over ten of thousands of miles with no lubrication in spite of all of natures attempts (lots and lots of riding in the rain).
I wonder why everyone does not implement that thought and practice?