TUN
9-6
* marked: In case of hard breathing, check the carburetor breather hoses for clogging.
Symptom
Setting
Checking
Closed to 1 / 4 throttle
Poor acceleration
White smoke
Use jet needle with a larger diameter.
Turn in pilot air screw.
Unstable at low speeds
Pinking noise
Lower jet needle clip position.
(1 groove down)
Turn in pilot air screw.
Poor response at extremely low
speed
Reduce pilot jet calibration No.
Turn out pilot air screw.
If not effect, reverse the above procedures.
Dragging brake
Overflow from carburetor
Poor response in the low to
intermediate speeds
Raise jet needle clip position.
If this has no effect, lower the jet needle
clip position.
Poor response when throttle is
opened quickly
Check overall settings.
Use main jet with a lower calibration no.
Raise jet needle clip position.
Use jet needle with a larger diameter.
If these have no effect, use a main jet with
a higher calibration no. and lower the jet
needle clip position.
Check air filter for fouling.
Poor engine operation
Turn in pilot air screw.
Adjust the throttle stop screw.
Check throttle valve operation.
This should be taken simply for an example. It
is necessary to set the carburetor while check-
ing the operating conditions of the engine and
discoloration of spark plugs.
Normally, carburetor setting is made by means
of the main jet, jet needle clip position, pilot jet
and pilot air screw.
CHANGE OF THE HEAT RANGE OF SPARK
PLUGS
Judging from the discoloration of spark plugs,
if they are found improper, it can be corrected
by the following two methods; changing carbu-
retor settings and changing the heat range of
spark plug.
• In principle, it is advisable to first use spark
plugs of standard heat range, and judging
from the discoloration of spark plugs, adjust
carburetor settings.
• If the calibration No. of the main jet must be
changed by ±30, it is advisable to change
the heat range of spark plugs and newly
select the proper main jet.
Standard spark plug
BR10EG / NGK
(resistance type)
ENGINE
