Crankcase/Crankshaft System Descriptions - Honda Motorcycle Service Manual

SYSTEM DESCRIPTIONS
The crankshaft changes the reciprocating action of the piston
and connecting rod into rotary motion, so the energy can be
transmitted t o the clutch and transmission.
It is necessary that the reciprocating and rotating components
are properly balanced t o produce a smooth running engine.
Stresses on the components increase proportional with an in-
crease in rpm's.
- - - - -
Reciprocating movement
- - - -
1
Rotary movement
Because of this increased stress, it is critical that the balance is
maintained when components are replaced.
There are t w o types of crankshafts; the assembly type in
which the right and left crankshafts are assembled with the aid
of a crank pin, and the single unit type, in which a unibody
crankshaft is employed. In the case of the former, caution
should be exercised when handling it, because if it is dropped,
the crank pin will be knocked out of alignment.
The unit type employs plain-type main bearings.
While the crankshaft is designed to rest directly on the metal
bearing material, strictly speaking, the crankshaft and metals
are lubricated on their surfaces by an oil film.
Consequently, scratches, burrs or dust on the bearing surface
spoils the oil film, leading t o bearing seizure.
issernbly-type crankshaft
Crankshaft
/
cu
Jnit-type crankshaft
14-2
Date of Issue: Sep., 1988
O HONDA MOTOR CO., LTD.