Throttle cable

The throttle cable runs from the twist grip on the right handlebar to the carburettor slide or the throttle body on a fuel-injected bike. Some bikes have two cables: one to open and one to close.

What it does

Turning the grip pulls the cable and opens the throttle. A spring at the carburettor or throttle body pulls it shut when you let go. A little slack at the grip (free play) makes sure the throttle closes fully at idle and when you turn the bars. A dry, kinked or frayed cable can stick open, which is very dangerous.

Signs it is worn or failing

• Grip stays open or closes slowly: Throttle sticks. Stop riding until fixed.
• Too much slack before the engine responds: Throttle has too much free play.
• Idle rises when you turn the bars: Idle speed is too high.
• Stiff or gritty grip: Cable frayed or stiff.

When to replace it

Replace a cable with any broken strands, a kinked outer or one that stays stiff after cleaning and oiling.

What to match when buying

• Make, model and year. Length, end fittings, adjuster position and whether it is a single or a pull and return pair.
• Carburettor and fuel-injected versions of the same model often use different cables.
• Compare with the old cable before fitting. Cheap cables with rough inner wire stick in the outer.

Fitting notes

• Route the cable exactly as the old one. Turn the bars lock to lock with the engine idling: the idle must not change.
• Check the grip snaps shut in every bar position before riding.
• See Adjust throttle free play and Lubricate or replace the throttle cable.

Reference (K-Light 125)