Acceleration = (change in speed) / (time for the change)
Change in speed = (speed at the end) minus (speed at the beginning)
For your scooter . . .
Change in speed = (25 m/s) - (0) = 25 m/s
Time for the change = 4.0 seconds
Acceleration = (25 m/s) / (4.0 s)
Acceleration = (25/4) (m / s·s)
Acceleration = 6.25 m/s²
That's the acceleration the SCOOTER is capable of. The next question is: Are YOU capable of that much acceleration, or do you go tumbling off the back ?