I just got this atv the 4wheel drive works good. Til I lock all 4 wheels in then the motor cuts out. I unlock them and it runs fine.

 

How high are the rpms going before the motor cuts out? The button on the left handlebar above the start button and kill switch says rev override...that is an override to allow for higher motor revving while the front diff is locked. Try holding the button and see what you get! I just sold one of these quads...rarely ever used the diff lock and don't think that I ever used the rev override button! If you are running into the motor cutting out as soon as you are locking the front diff I would look towards the override button. Keep us posted as to what you find out!