Yamaha YZ250F(W) Owner's Service Manual page 640

1
SETTING
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 throttle
opening.
Select a leak jet having lower calibrating
No. than standard to enrich the mixture.
<Example> #80 → #70
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> #80 → #90
Standard leak jet
* Except for USA and CDN
7 - 8
T U N
#80
* #70