seizeup

Seizeup is a term that can refer to several distinct concepts, primarily within the realm of motorcycling and older mechanical devices.

In the context of motorcycles, particularly older or carbureted models, "seizeup" describes a catastrophic engine failure. This occurs when the engine overheats to a critical point, causing the internal components, such as the piston and cylinder wall, to expand beyond their normal tolerances. This expansion can lead to the piston becoming permanently stuck or "seized" within the cylinder, preventing the engine from rotating. The causes of a seizeup are typically a lack of lubrication, prolonged high-speed operation without adequate cooling, or a fuel-air mixture that is too lean, leading to excessive combustion temperatures. Repairing a seized engine usually involves significant internal component replacement or an entire engine rebuild.

Beyond motorcycles, "seizeup" can also refer to the jamming or locking of any mechanical part due to friction, corrosion, or debris. This might happen with gears, bearings, or other moving components in various machinery. Similar to an engine seizeup, it indicates a failure of the part to move freely, often requiring disassembly and repair or replacement.