Effects Of The Setting Parts On The Throttle Valve Opening; Main Jet Adjustment; Pilot Air Screw Adjustment; Pilot Jet Adjustment - Yamaha YZ125 Owner's Manual

EAM30593
EFFECTS OF THE SETTING PARTS ON THE
THROTTLE VALVE OPENING
A. Closed
B. Full-open
1. Pilot air screw
2. Pilot jet
3. Jet needle
4. Diameter of straight portion
5. Clip position
6. Throttle valve
7. Main jet
EAM30594

MAIN JET ADJUSTMENT

The richness of air-fuel mixture with 1/2–4/4
throttle can be set by changing the main jet "1".
Standard main jet
1. Spark plug is too hot.
Select a main jet having higher calibrating
No. than standard. (To be enriched)
2. Spark plug is wet.
Select a main jet having lower calibrating No.
than standard. (To be leaned out)
EAM30595

PILOT AIR SCREW ADJUSTMENT

The richness of the air-fuel mixture with the
throttle fully closed to 1/4 open can be set by
turning the pilot air screw "1".
Turning in the pilot air screw will make the mix-
ture enrich at low speeds, and turning it out will
lean it.
Standard pilot air
EAM30596

PILOT JET ADJUSTMENT

The richness of air-fuel mixture with the throttle
fully closed to 1/2 open can be set by turning the
pilot jet "1". It is changed when adjustment can-
not be made by the pilot air screw alone.
A larger size jet results in a richer mixture at low
#430
speeds, and a smaller size in a leaner mixture.
Standard pilot jet
8-2
screw position
ENGINE
2-1/4 turns out
#40