Yamaha YZ250(P)/LC, Owner'S Service Manual

Page: 532 / 584

7-4
SETTING
TUN
EC71R000
Pilot jet adjustment
The air-fuel mixture can basically be adjusted by
the pilot air screw from full closed to 1/8 throttle.
If the pilot air screw is not enough for this adjust-
ment, the pilot jet
1
is changed.
A larger size jet results in a richer mixture at low
speeds, and a smaller size in a leaner mixture.
EC718001
Jet needle groove position adjustment
Should the engine be hard to run smoothly at
intermediate speeds, the jet needle
1
must be
adjusted. If the mixture is too rich or too lean at
intermediate speed operation, irregular engine
operation and poor acceleration will result.
Whether or not the richness of the mixture is
proper is hard to be determined by means of the
spark plug and therefore, it should be judged
from your feeling of actual engine operation.
*For EUROPE
Standard pilot jet
#50
*#52
EC716001
Pilot air screw adjustment
The richness of air-fuel mixture with full closed to
1/8 throttle can be set by turning the pilot air
screw
1
.
Turning in the pilot air screw will enrich the mix-
ture at low speeds, and turning out it will lean out
the mixture.
*For EUROPE
*For EUROPE
Standard pilot air
1 turn out
*1-3/8 turns out
screw position
(for reference only)
Standard clip position
No.2 groove
*No 3 groove
5NX-9-30-7 6/5/01 4:47 PM Page 8