This series of engines are usually to be found on ride on lawnmowers but can also be found on industrial walk behind mowers, rotorvators 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. There are electric start and pull start versions. Some of these engines have both.
They may have an integral fuel tank fitted to the R/H side of the engine but often the tank is provided by the mower manufacturer and is seperate from the engine.
The Model, Type and Code numbers are stamped into the pressed steel cowling just above the spark plug location and are typically 170702, 170707, 171702, 190702, 190707, 196707 etc. Engines whos model begins with 17 are 7HP, those begining 19 are 8HP.