Could be a plugged up fuel filter.
You must have a ignition problem
That could be the cam shaft position sensor.Check that out>
He keeps driving.
Get rid of it
The engine shutting off could be the control module or the pickup coil within the distributor. The steering wheel locks???
If it is cutting out and the fan is working and it has proper air for cooling means it is damaged inside and need to be replaced or repaired
either its low or too high of pressures
fuel rail sensor
If your Yamaha TTR 250 starts but keeps cutting out after a fuel minutes, it might not be getting enough fuel. Check to ensure the fuel line is not clogged.
An Abstract is a printout of your driving record for as long as the Government keeps infractions and accidents on file.
dont press the break pedal so much
Check the connections on the wheel sensors.