OBD port YAMAHA WR 450F 2005 Owners Manual

7 - 5
TUNSETTING
Jet needle groove position adjustment
NOTE:
For setting adjustment, replace the standard
jet needle with the one designed for setting.
Adjusting the jet needle 1 position affects the
acceleration when the throttle is 1/8 to 3/4
open.
1. Too rich at intermediate speeds
Rough engine operation is felt and the
engine will not pick up speed smoothly. In
this case, step up the jet needle clip by one
groove and move down the needle to lean
out the mixture.
2. Too lean at intermediate speeds
The engine breathes hard and will not pick
up speed quickly.
Step down the jet needle clip by one
groove and move up the needle to enrich
the mixture.
Effects of changing the jet needle groove
position (reference)
ÈIdle
ÉFully open
1No.5 groove
2No.3 groove
3No.4 groove
Jet needle adjustment
The jet needle is adjusted by changing it.
The tapered sections of all jet needles have
the same starting positions, but the needles
are available with different straight-portion
diameters.

OBDUS - 4
Clip position
Diameter
a of straight portion Supplied jet needle OBDUS
1/4 1/2 3/4
+10%
–10%
1
23
É È