From OCAU Wiki
Aftermarket: An accessory, or part, made for your motorcycle by someone other than the original manufacturer.
Air/fuel ratio: The mixture of fuel and air produced by carburetion or fuel injection. A comparison between the amount of air and amount of fuel going into the combustion chamber.
Airhead: A BMW that is mostly cooled by air and not by water or oil. The name of a major BMW club.
Allen key: A type of hexagonal shaped wrench.
Amps: Short for ampere, the unit of measure of the flow of electrical current.
AMF: American Machine and Foundry. Better known for ten pin bowling alleys. Owned Harley Davidson between 1969 1981. Made some of the worst motorcycles ever. Even Triumph [in the same era] couldn't compete with their poor quality control.
Anti-seize compound: A somewhat greasy paste that is added to threads to keep them from sticking.
Ape Hangers: Really high handlebars, mostly on choppers.
ATE: Made the first disc brake for BMW in 1974 with the /6 series. They were well known for not working well. In fact, the single disc did not work nearly as well as the former drum brake of the /5 series.
Babbit: The bearing compound found in plain crankshaft bearings.
Back roads: Off the main highway, often preferred by motorcyclists.
Balaclava: A head and neck "sock" with mouth and eye slits.
Balancing carbs: The procedure for getting two or more carbs tuned properly to allow smooth running of the engine.
Basket case: A motorcycle that has been taken apart and thus is in pieces. For the person who still expects to put it back together, it is a project, but the buyer calls it a basket case.
Bearing has flat spots: See "bearings are notched" below.
Bearing preload: The slight pressure holding tapered bearings together.
Bearing race: One of the two bearing surfaces that balls or rollers ride against.
Bearing spun: A bearing can spin in the case that is supposed to hold it. This may damage the case, or aluminum hub.
Bearings are notched: Ball or roller bearings can get worn spots on them that are felt easily. Those are flat spots.
Beemer: a slang term for a BMW motorcycle. Often confused with Bimmer which is slang for a BMW car.
Beeza: a slang term for a BSA motorcycle.
Banana seat: A long seat for two people.
Big Ends: The larger ends of the connecting rods which attach to the crankshaft of the engine.
Biker: An "image" of a person who rides a motorcycle, often limited to those not quite fitting the outlaw image.
Bikie: An "image" of a person who rides a motorcycle, often limited to those fitting the outlaw image.
Bikini fairing: A very short and small fairing, typically mounted to the front-end of the machine rather than the frame, more for style than function.
Bimmer: A slang term for a BMW car.
Bottom end: The crankshaft, crankshaft bearings, journals, webs and connecting rod lower ends of an engine. An engine is considered to have a top end and a bottom end.
Boxer: A slang term for an horizontally opposed engine where each piston has its own crank pin. The term comes from the image of the two pistons traveling towards each other and looking like boxers fighting.
Brain: The small computer which controls engine, steering and brake functions on most motorcycles. Generally located somewhere between the hands and feet of the rider. May be in the head, often in the arse.
Brake pads vs. shoes: A disc brake uses pads for the friction material and a drum brake uses shoes.
Brake squeal: A loud squeal coming from the brake.