Yamaha YZ450F(W), Owner'S Service Manual

Page: 608 / 650

7 - 4
T U N
SETTING
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.
Main jet adjustment
The richness of the air-fuel mixture at full throt-
tle can be set by changing the main jet
1
.
If the air-fuel mixture is too rich or too lean, the
engine power will drop, resulting in poor accel-
eration.
Effects of changing the main jet (reference)
È
Idle
É
Fully open
Standard main jet #160
1/4 1/2 3/4
+10%
#160
–10%
#162
#158
È É