This series of engines are usually to be found on ride on lawnmowers but can also be found on industrial walk behind mowers, paddock cleaners (poo pickers) and other equipment.
They have side valve (L-Head) configuration with the spark plug near the centre of the cylinder head.
The head is flat with vertical cooling fins and often has a flat, pressed steel cover plate over most of the fins with a hole for spark plug access
The carburettor and air filter are fitted to the L/H side of the engine (viewed from behind) with the exhaust emerging from below the carburettor manifold.
They are usually electric start but there are also pull start versions. Some of these engines have both.
The Model, Type and Code numbers are stamped into the pressed steel cowling just above the spark plug location or on a small plate rivited to the top and are typically 220707, 251707, 280707, 281707, 286707, 28M707, 280T707, etc.
Engines whos model begins with 22 are 10HP, those begining 25 are 11HP, those starting 28 are 11.5HP - 13HP depending upon particular model and type.