Yamaha WR250F(N) Owner's Service Manual page 646

1
SETTING
Jet needle adjustment
The jet needle is adjusted by changing it.
Standard jet needle
* For EUROPE
** For CDN, ZA, AUS and NZ
The tapered sections of all jet needles have
the same starting positions, but the needles
are available with different straight-portion
diameters.
<Example>
OBELP - 4
Leak jet adjustment (accelerator pump
adjustment)
The leak jet 1 is a setting part that adjusts the
flow of fuel discharged by the accelerator
pump. Since the accelerator pump operates
only when throttle is open, the leak jet is used
to adjust a fuel mixture ratio for quick throttle
opening and is therefore different from other
setting parts that adjust a fuel mixture for each
throttle opening (each engine speed).
1. The engine breathes hard in quick throt-
tle opening.
Select a leak jet having lower calibrating
No. than standard to enrich the mixture.
<Example> #105
2. Rough engine operation is felt in quick
throttle opening.
Select a leak jet having higher calibrating
No. than standard to lean out the mixture.
<Example> #105
Standard leak jet
* For EUROPE
** For CDN, ZA, AUS and NZ
7 - 7
T U N
OBELP
*OBEGP
**OBEHP
Clip position
Diameter a of straight portion
#95
#115
,
* ** #105
#60