Abstract: An improved low heat rejection high efficiency engine system for an insulated two stroke internal combustion engine which includes an insulation component provided in association with at least one combustion chamber in order to minimise heat loss during operation, the system having at least one inlet port fluidly connected to a transfer port from a pumping cylinder for inlet of a fresh charge in an induction portion of the operation cycle, the inlet port opened and closed during the operation cycle by an inlet valve, characterized in that the period for which the inlet valve is open during the operation cycle is less than 180° of rotation.