Motorcycle Glossary of Terms
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Octane - The measure of
a fuel's resistance to knock.
OEM - Original Equipment
Off-road bike - Motorcycle
designed for off-road use, not necessarily
OHC - Overhead cam engine.
Ohm - The unit of electrical
resistance. Ohms = Volts/Current.
Ohmeter - An instrument
for measuring electrical resistance.
Oil cooler - System for
diverting engine oil outside of the engine
to a radiator for cooling purposes.
Oil injection - A system
of two-stroke engine lubrication where oil
is pump-fed to the engine in accordance with
Open circiut - Am electrical
condition where there is a break in the flow
of electricity - no continuity (high resitance).
O-ring - A type of sealing
ring made of a special rubber-like material;
in use, the O-ring is compressed into a groove
to provide the sealing action.
Overhead cam - An engine
with overhead camshaft or camshafts operating
Overhead valve - A valve
mounted in the cylinder head.
Oversize (OS) - Term used
for piston and ring size options fitted to
a rebored cylinder.