The air-cooled single-cylinder, four valve OHC, stroke volume 499 ccm, the bore 90,00mm and stroke 78,50 mm. The crankcase, cylinder head and cylinder are made of Aluminium alloy. Cylinder has nicasil only. We not supply the overbore cylinders. The crankshaft and connecting rod big-end have cage-type needle bearings. The chain driven camshaft is supported in the cylinder head on needle bearings. The valves operated by rocker arm are at an angle 35°. The valve seats are hotpressed into the cylinder head. The pistons is a light alloy forging and carries two piston rings, first 1mm compression ring and seconnd 2 mm oil control ring. The circulation-system of lubrication is used. The oil tank is situated in the space between the valve gear cover and R.H. ofthe crankase, the iol filing is 0,7 l for new engine and 0,65 l is refill between heats. The level cam be checked by the oil level indicator. The engine is intended for the carburettor of diameter 34 mm and provided with electronic ignition.