OBD port YAMAHA WR 400F 2000 Owners Manual

7 - 6
TUNSETTING
Jet needle adjustment
The jet needle is adjusted by changing it.
* Except for USA
The tapered sections of all jet needles have
the same starting positions, but the needles
are available with different taper angles and
straight-portion diameters.

OBDRS - 3
Clip position
Diameter a of straight portion
Taper angle b Standard jet needleOBDRS
*OBDRQ
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.
Idle
õFully open
(Taper)
A smaller taper affects the richness of the air-
fuel mixture when the throttle is fully open. To
change the air-fuel mixture only at 1/2 throttle,
also adjust the main jet.
Idle
õFully open
1/4 1/2 3/4
+10%
S
–10% AB
T
R
1/4 1/2 3/4
+5%
D
–5% AB
C
E