Jet Needle Adjustment; Effects Of Changing The Jet Needle (Reference) - Yamaha YZ250F(V) Owner's Service Manual

SETTING

Jet needle adjustment

The jet needle is adjusted by changing it.
Standard jet needle
* Except for USA and CDN
The tapered sections of all jet needles have
the same starting positions, but the needles
are available with different straight-portion
diameters.
<Example>
OBELQ - 3
Effects of changing the jet needle (refer-
ence)
(Diameter of the straight portion)
Changing the diameter of the straight portion
adjusts the air-fuel mixture when the throttle is
1/8 to 1/4 open.
È
1/4
È Idle
É Fully open
7 - 7
T U N
OBELQ
* OBEKP
Clip position
Diameter a of straight portion
1/2 3/4
P
R
É
+10 %
Q
–10 %