Motorcycle Glossary

Saddle Tank A fuel tank that fits over the top tube of the frame.

Scooter Small-wheeled utilitarian machine with a step-thru frame.

Sender A sensor unit conveying information about an engine to a gauge warning light, or other component.

Servo Any system used to assist a mechanism to operate with greater force than that initially applied to it.

Side Valve Valves positioned at the side of a cylinder.

Simplex Single, on of. Usually applied to frames with a single downtube.

Skirt The part of a component that hangs down, particularly the area of a piston.

Snail-Cam Chain Adjuster Axle-mounted helical cams that allow accurate chain adjustment.

S.O.H.C. Single overhead camshaft.

Speedway Specialised sport run on short, oval dirt tracks with four riders from two teams in each race.

Spine Frame A frame with a single main structural member from which the engine is suspended.

Split Single A two-stroke engine with two pistons that share a single combustion chamber.

Step-Thru A frame layout with a low structure between the seat and the steering head. On early machines it was commonly called an open frame.

Stressed Member A component that is an integral part of the whole structure.

Stroke Measurement of length of piston travel in the bore, usually expressed in millimetres (see also bore).

Subframe Any auxiliary framework attached to the main body of a vehicle. On a motorcycle this often refers to the rear section of the frame, which supports the seat etc.

Supercharger Mechanically powered device that compresses the combustible charge into the cylinder, artificially increasing the compression ratio. When the "blower" is driven by exhaust gas, the device is called a turbocharger.

S.V. See side valve.

Swept Volume The volume displaced by a piston′s travel.

Swingarm Suspension member pivoted at one end and supporting the wheel at the other. In most cases the swingarm is more accurately described as a pivoted fork, as the wheel is supported at both sides.