VESPA GTV 125, Service Station Manual

Page: 41 / 278

Checking the spark advance
- To check ignition advance, use the stroboscopic
light with induction pincers connected to the spark
plug power wire.
- Connect the induction pincers being careful to
respect the proper polarity (the arrow stamped on
the pincers must be pointing at the spark plug).
- Place the light selector in central position (1 spark
= 1 crankshaft revolution as in 2 T engines).
- Start the engine and check that the light works
properly and the rpm indicator can read also the
high rpm (e.g. 8000 rpm).
- If flash unsteadiness or revolution reading error
is detected (e.g. half values), increase the resistive
load on the spark plug power line (10 ÷ 15 K
Ω
in
series to AT cable).
- Remove the plastic cover from the slot on the fly-
wheel cover.
- Operating on the flash corrector displacement of
the bulb, make the reference on the flywheel cover
coincide with level on the water pump drive. Read
the advance degrees indicated by the stroboscop-
ic light.
- Check that the advance degrees corresponds
with the rotation rpm as indicated in the table.
- If there are anomalies, check the Pick-Up and the
control unit power supply (positive-negative), re-
place the control unit if necessary.
- The brand new control unit prevents that the en-
gine rotation exceeds 2000 rpm.
- The programmed control unit allows the engine
to rotate within the prescribed limits.
Characteristic
Ignition advance
10° ± 1° at 2,000 rpm
Vespa GTV 125
Maintenance
MAIN - 7