Pilot Jet Adjustment; Jet Needle Groove Position Adjustment - Yamaha YZ250(N)/LC Owner's Service Manual

Table of Contents

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

Turning in the pilot air screw will enrich the mix-

ture at low speeds, and turning out it will lean out

the mixture.

Standard pilot air

screw position

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.

Standard pilot jet

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.

Standard clip position

*1-3/4 turns out

(for reference only)

*No 3 groove

Show Quick Links

Table of Contents