Motorcycle Glossary of Terms
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ABI - Association of British
ABS (Anti-lock braking system)
- A system usually electronically controlled
, that senses incipient wheel lockup during
braking and relieves hydraulic pressure at
wheel which is about to skid.
ACU - Auto Cycle Union,
who control a large part of British Motorcycle
Advanced Ignition - Ignition
timing set causing firing before the piston
reaches centre top, variation is now automatic.
Aftermarket - Components
suitable for the motorcycle, but not produced
by the motorcycle manufacturer.
AHRMAL - American Historic
Racing Motorcycle Association.
Air-cooling - Many motorcycles
rely on air-cooling to the atmosphere.
Air intake - The carburettor
port admitting are to mix with fuel from the
AJ - Common term for an
Allen key - A hexagonal
wrench which fits into a recessed hexagonal
Alternating current (ac)-
Current produced by an alternator. Requires
converting to direct current by a rectifier
for charging purposes.
Alternator - Converts mechanical
enery from the engine into electrical energy
to charge the battery and power the electrical
AMA - American Motorcycle
AMCA - Amateur Motor Cycle
Association, promoters of English off-road
Ampere (amp) - A unit if
measurement for the flow of electrical current.
Current = Volts /Ohms.
Ampere-houe (Ah) - Measure
of battery capacity.
Angle-tightening - A torque
expressed in degrees. Often follows a conventional
tightening torque for cylinder head or main
Antifreeze - A substance
(usually ethylene glycol) mixed with water,
and added to the cooling system, to prevent
freezing of the coolant in winter. Antifreeze
also contains chemicals to inhibit corrosion
and the formation of rust and other deposits
that would tend to clog the radiator and coolant
passages and reduce colling efficiency.
Anti-dive - System attached
to the fork lower leg (slider) to prevent
fork dive when braking hard.
Anti-seize compound - A
coating that reduces the risk of seizing on
fasteners that are subjected to high temperatures,
such as exhaust clamp nuts and bolts.
APCO - The Association of
Public Safety Communications Officials - International.
Apex - The middle or centre
point of a corner.
API - American Petroleum
Institute. A quality standard for 4-stroke
APMC - The Association of
Pioneer Motor Cyclists.
Asbestos - A natural fibrous
mineral with great heat resistance, commonly
used in the composition of brake friction
materials. Asbestos is a health hazard and
the dust created by brake systems should never
by inhaled or sigested.
ATF - Automatic Transmission
Fluid. Often used in front forks.
ATU - Automatic Timing Unit.
Mechanical device for advancing the ignition
timing on early engines.
ATV - All Terrain Vehicle.
Often called a quad.
Auto Cycle Club - Formed
in 1903, it was the original governing body
of motorcycle sport, in 1907 became the Auto
Autocycle - A 98cc moped.
Automatic inlet valve -
Activated by the engine suction. Forerunner
of the mechanically operated valve.
Axial play - side-to-side
Axle - A shaft on which
a wheel revolves. Also know as a spindle.
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