Yamaha TZ125M1 Owner's Service Manual page 240

SETTING
EC71B030
Relationship with throttle opening
The flow of the fuel through the carburetor
main system is controlled by the main jet and
then, it is further regulated by the area
between the main nozzle and the jet needle.
On the relationship between the fuel flow and
the throttle opening, the fuel flow relates to the
jet needle straight portion diameter around 1/8
throttle opening, whereas around 1/4 to 1/2
throttle opening it relates to the taper starting
position and to the clip position.
Therefore, the fuel flow is balanced at each
stage of throttle opening by the combination of
the jet needle straight portion diameter, taper
starting position and clip position.
Example:
N8WW-3rd groove
N8VW-3rd groove
N8VH-2nd groove
N8VH-3rd groove
A Lean (larger diameter)
B Rich (smaller diameter)
1 1/8 throttle
2 1/4 throttle
3 1/2 throttle
a Main nozzle
EC71H031
Other setting parts
1. Power jet 1
Use a power jet of a smaller size if in the
main jet adjusting, no good response is
achieved just after shifting up gear even
though the engine is running properly and if
there is an allowance for the discoloration
of the spark plug(s) and piston(s).
w
A larger size results in a richer mixture and
a smaller size in a leaner mixture around
12,000 rpm.
Factory-set power jet
7-6
TUN
#60