If you mount the engine on it's side, you can help minimize the evils
of a non-pressurized system. Some engines....four strokes especially,
can run fine without pressure....mainly due to the fact that the carb is
located close to the centerline.

An upright mounted two stroke will be troublesome without pressure.
I might consider an inverted two stroke without pressure, living on an
abundance of gravity flow.....

....but given the choice, I'll go with the pressure. [sm=thumbup.gif]

FBD.