Yamaha YZ250F(W) Owner's Service Manual page 630

T U N
SETTING
Effects of the setting parts on the throttle
valve opening
1
2
3
4
1/8 1/4
È 1/2 3/4 É
È Closed
É Fully open
1 Pilot screw/pilot jet
2 Throttle valve cutaway
3 Jet needle
4 Main jet
Main system
The FLATCR carburetor has a primary main
jet. This type of main jet is perfect for racing
machines since it supplies an even flow of fuel,
even at full load. Use the main jet and the jet
needle to set the carburetor.
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.
7 - 3