I assume this is happening when using gamepad? As far as I remember, Gamepad.Axis expression returns a number from -1 to 1. So your maximum speed changes from negative 3 to 3. You need to multiply by at least 100 and use abs() expression.
Also, I recommend using Browser Log to debug problems like this. If you'd tried adding "Browser Log GamePad.Axis(0,0)" into this event, you would immediately understand what's going on.