Yamaha WR250F(N), Owner'S Service Manual

Page: 638 / 686

7 - 3
T U N
SETTING
Effects of the setting parts on the throttle
valve opening
Å
Closed
ı
Fully open
1 Pilot screw/pilot jet
2 Throttle valve cutaway
3 Jet needle
4 Main jet
4/4
3/4
1/2
1/4
1/8
0
ı
Å
1/2 3/4 1/4 1/8
1
2
3
4
Å ı
Main system
The FLATCR carburetor has a primary main
jet. This type of main jet is perfect for racing
motorcycles since it supplies an even flow of
fuel, even at full load. The main air jet has
almost no effect on the air-fuel mixture. Use
the main jet and the jet needle to set the car-
buretor.
Pilot system
The FLATCR carburetor is manufactured with
a pilot screw. The pilot screw adjustment
ranges from fully closed throttle to 1/4 open
throttle.