A Woodruff key is a finely machined metal piece used to connect a rotating device to a shaft. The distinction of a Woodruff key is that it is machined to fit into a semi-circular pocket, which eliminates the necessity of cutting or milling a keyway the length of a shaft, greatly increasing the strength of the shaft. It was created by W.N. Woodruff of Connecticut in the late 1800s. In 1888, W.N. Woodruff was awarded the John Scott Medal by the Franklin Institute for the invention of what would forever be known as the “Woodruff key.”

A Woodruff key and its corresponding keyway in the crankshaft of a Yamaha XT250.

The electrical wires that make up the electrical systems of a motorcycle are bundled together and encased in a protective sleeve (known as loom or conduit) to form what is known as the wiring harness. Different color wires are used for different components to make electrical testing and troubleshooting easier, and bundling the wires keep them protected and compact.

A multi-plate motorcycle clutch fitted inside the engine which runs in an oil bath.

A pump that circulates coolant through a water-cooled motorcycle engine. Typically uses an impeller to force the coolant through the body of the water pump.