Yamaha NMAX 155 Owner's Manual page 52

Instrument and control functions
Place vehicle on centerstand.
Turn the main switch on.
Put the sidestand up.
6
Push the start switch while applying
either of the brake levers. The engine will
start.
Put the sidestand down.
If the engine stalls:
The sidestand switch is OK.
WARNING
The vehicle must be placed on the
centerstand during this inspection.
If a malfunction is found, have the vehicle
inspected before riding.
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