TOHATSU NB-1000 Service Manual page 42

8/9.8 Models
Throttle Setting
Engine
8
9.8
4
The 8 and 9.8 engines are different electronically from other
4
one and two cylinder engines. The 8 and 9.8 engines
incorporate an electronic switch (Thyristor SCR (Silicon
Controlled Rectifier)) which is actuated by signal voltage to provide
stable, high performance secondary sparking.
The magneto is a simultaneous, multi-cylinder ignition type and
would, if allowed, cause ignition in both cylinders at the same time.
Ignition however occurs only on the compression stroke side (TDC
side). Ignition is caused in only one cylinder at each spark timing.
The other cylinder is not ignited, although sparking is caused in both
cylinders at the same time.
The timing is adjusted only after the powerhead has been
disassembled and reassembled. Timing is controlled by the position of
the advancer link rod which is adjusted so that the coil plate turns
counterclockwise to contact with the stopper when the throttle valve is
closed fully when the advancer lever is moved.
8/9.8 Adjustment Procedure
1. Move the advancer lever with a finger to fully open the
carburetor throttle valve. At this time, adjust the length of pole
joint cap of the advancer link rod so that the coil plate stopper
hits the projection of the set plate lower as the coil plate rotates to
the left.
2. Assemble the throttle cable into the throttle drum and attach
the nut to the throttle cable holder of the motor cover lower. At
this time, be careful that the cable is not attached to a wrong
location.
3. Adjust the nut of the throttle cable that was attached to the
throttle cable holder so that the coil plate of the magneto rotates
to the left at the position where the handle grip stops when it is
turned to the left and hits the coil plate stopper, and then the coil
plate of the magneto rotates to the right at the position where the
handle grip stops when it is turned to the right and hits the coil
plate stopper.
1-/ 2-Cylinder
GENERAL SERVICE INFORMATION
Full Open
Match Mark Target RPM
BTDC 22° 4500 - 5500
BTDC 26° 5000 - 6000
Full Closed (In Gear)
Match Mark Target RPM
ATDC 1.5°
BTDC 2.5°
750
750
T1971
2-33