System for a two-stroke combustion engine with controlled additional air

A system (1) for supplying an air-fuel mixture to a two-stroke internal combustion engine (2), comprising a carburettor (3) having a throttle valve (4) and a choke valve (5), said system further has a transfer passage (6) between a crankcase (7) chamber and a combustion chamber (8) of said engine (2), wherein a supply conduit for additional air (9) having an air valve (10) for said additional air, said supply conduit for additional air (9) being adapted to discharge the additional air into the top portion of said transfer passage (6), either directly through a check-valve or via a recess in an engine piston (26), during a portion of a cycle of said two-stroke internal combustion engine (2),

• characterised in that said air valve (10) is controlled by said throttle valve (4) so as to affecting an air valve opening state when said throttle valve opening state is affected,
• and in that the opening state of said air valve (10) is delimited by a choked state of said choke valve (5) regardless of the throttle valve opening state.