Abstract: A jet-stream control combustion engine comprising an auxiliary intake system in a cylinder head leading to an internal combustion chamber, besides an intake system and an exhaust system. The auxiliary intake system is equipped with a hollow cylindrical jet piece fitted into a through-hole from the combustion chamber side, a hollow cylindrical jet body fitted from the opposite side of the through-hole, and an auxiliary intake passage opened and closed by a jet valve fitted inside of the jet body, wherein the auxiliary intake passage communicates with the internal combustion chamber via an injection chamber formed in the jet piece and an injection port thereof. The jet piece and the jet body are screwed and fixed relative each other in such a way as to compressibly contact with receiving surfaces of the cylinder head, so that the structure gets simplified and facilitates to assembly and disassembly with high parts-interchangeability.