Kubota J106-STD Operator's Manual page 42

26 OPERATING THE GENERATOR
3. After stopping the engine, make sure that the door is
closed and the main switch (key) is at "OFF".
4. The following causes are possible for such unusual
engine shut-off.
Pinpoint and correct the cause of trouble.
A Check for the stop solenoid.
A Check to see if the battery has discharged too
much or is in trouble.
A Check for disconnection of the battery terminals.