Yamaha TZ250M1, Owner'S Service Manual

Page: 271 / 287

SETTING
7-7
EC71H040
Other setting parts
1. Power jet
1
Power jet is not basically changed. Since
the areas of the main jet and main nozzle
overlap each other, special knowledge is
required for a setting change.
A larger size results in a richer mixture and
a smaller size in a leaner mixture.
Factory-set power jet #55
w
2. Pilot jet
1
The pilot jet is used in relation to the engine
response at small throttle opening. This is
changed when the main nozzle setting is
not enough.
A larger size results in a richer mixture and
a smaller size in a leaner mixture.
Factory-set pilot jet #30
w
3. Pilot air screw
1
The pilot air screw relates to the engine
response at a smaller opening than for the
pilot jet.
This setting may be changed for want of
time or in emergency, but it is basically set
at the factory-set pilot air screw position.
Factory-set pilot air
1-1/2 turns out
screw position
w
4. Spark plug
The spark plug heat range is not basically
changed.
Constant attention to the discoloration of
the spark plug and piston head will enable
you to tell to some extent whether the set-
ting is good or bad.
Standard spark plug R6179A-105P/NGK
w
NOTE:
For the effects each setting part has, refer to
“Effects of setting parts in relation to throttle
valve opening” (P7-2).
TUN