The market for handheld engines such as chainsaws, brush-cutters and for 2-wheeler applications like scooters, mopeds and minimum transportation vehicles shows a strong tendency towards 4-stroke application due to environmental and image reasons. The ranking of the priorities like Weight - Cost - Performance in these engines differs and beside this the fulfillment of the legal requirements for pollutant emission, noise and the expected fuel economy lead to a different approach for the layout of the cylinder-heads showing different optimum solutions dependant on the casting technology, whether pressure die cast or with sand cores. The variations include the number of valves from two to four and the arrangement of the valves and spark plugs. The porting and combustion chamber layout, including data for flow rate and charge movement concepts, are stipulated for the cylinder bore of 41 mm. The 1-D Thermodynamic BOOST simulations indicate the predicted potential which is compared in a benchmark to present 4-stroke engines on the market.