Description Of Operation - TOHATSU NB-1000 Service Manual

DESCRIPTION OF OPERATION

The power head of this outboard motor is a two-
1 2
stroke engine (or two-stroke cycle engine). The
engine completes its one cycle operation including gas mixture
suction, compression, explosion and exhaust while the crankshaft
rotates once i. e. the piston moves upward and then downward
(two strokes).
As the piston starts to move toward top dead center (TDC), the
interior of the crank case is made vacuum pressure causing the
reed valve to open and the gas mixture to be taken into the
crankcase. As the piston comes near the TDC, the spark plug
produces the sparks to ignite the compressed gas mixture for
combustion. As the fuel mixture is exploded, the piston moves
toward bottom dead center (BDC) and open the exhaust port and
then scavenging port. The scavenging is an action that sends the
fresh gas mixture in the crankcase to the cylinder.
1-/ 2-Cylinder
POWERHEAD
T1674
T1675
4-7