KYMCO Sento 50 Owner's Manual page 25

(3) USE THE STARTER BUTTON
Push the starter button without rotating the throttle grip.
If the engine fails to start after the starter button is pressed
for 3～4 seconds when it is warm, rotate the throttle grip
for 1/8～1/4 turn to facilitate starting.
When the motorcycle is not used for a long time or the
fuel tank is empty, if the engine is still hard to start after
the fuel tank is refilled with gasoline, slightly turn the
throttle grip and press the starter button for several times to
start the engine.
In order to avoid battery overcharge, do not press the
starter button more than 5 seconds.
If the engine does not start after the starter button is
pressed for 5 seconds, wait for more than 5 seconds and
then press the button again or start the engine by the kick
lever.
※ CAUTION:
Don't press the starter button while the engine is running;
otherwise the engine will be damaged.
When starting the engine, the rear brake lever must be
applied to connect power and the stoplight will come on
when power is connected.
20