Jet Needle Groove Position Adjustment; Effects Of Changing The Jet Needle Groove Position (Reference); Jet Needle Adjustment - Yamaha WR450F(V) Owner's Service Manual

SETTING

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)
È
1/4
1
2
È Idle
É Fully open
1 No.5 groove
2 No.3 groove
3 No.4 groove

Jet needle adjustment

The jet needle is adjusted by changing it.
Supplied jet needle
The tapered sections of all jet needles have
the same starting positions, but the needles
are available with different straight-portion
diameters.
<Example>
OBDUS - 4
7 - 5
T U N
1/2 3/4
OBDUS
Clip position
Diameter a of straight portion
É
+10%
3
–10%