You have not described what, if any, maintenance that you have done or regularly do, and what parts you may have replaced, if any. Also the conditions under which the engine stops, i.e. sitting at idle, cruising, or wide open throttle. Without such information the incredibly helpful people on this board can only guess.
I, not being one of the incredibly helpful people on this board, can only say that when something similar happened to me, it turned out to be a dirty fuel filter that needed to be replaced. That is, of course, only a guess based on my personal experience and not enough information.