A molded coverseat secures over an opening in a carrying box on a two-wheeled cart to serve as a cover and a seat. An extended-width result is obtained by combining a rotation result with a shift result in accordance with a mask that is selected in response to at least a portion of the value of the degree to which a data word is to be shifted. The reformer draws oxygen from the engine exhaust rather than ambient air as in the prior art. The gearbox further includes a casing and the electric machine is inserted and fixed into a seat formed by that casing.