Both are needed to get your bike moving. But what
is it?
Pre-unit just & Unit construction is
Pre-unit just means that the engine crankcase and gearbox are two separate
units bolted into the same frame, whereas unit construction means the
gearbox and crankcase share the same casing.
Early motorcycles were
largely pre-unit as it was simpler to cast gearbox and engine casings
separately at the foundry, and manufacturers could buy in engines and/or
gearboxes and pair them up without any major issues.
Unit construction is used for essentially all modern motorcycles, it
results in a lower total weight, much better rigidity, fewer places to
leak oil, and improved simplicity.
A valve opening under vacuum to allow fuel/air mixture
to enter the crank of a 2-stroke
RFVC
The RFVC indication on the head off the engine means: Radial Four Valve
Combustion. RVFC or
Radial Four Valve Combustion was a proprietary valve
arrangement created by Honda to make a four valve head flow more
like a hemi head. The splayed valves arrangement allows quicker
flame propagation across the combustion chamber, allowing the
engine to produce more power at a given RPM.
Dry weight is what the bike weighs without fluids - without gas, oil,
coolant, final drive fluid, or sometimes even the brake fluid and
battery. Motorcycles are typically shipped dry for ease of
handling and safety.
Wet weight/curb weight is a term used to
refer to the weight of a motorcycle when it has been loaded with all the
fluids it needs to operate, along with the battery. Generally only
a half tank of gas, ready to ride.
But these terms are not standardized across the industry.