PURPOSE: To prevent altering operation of various kings of restriction shafts certainly, and enable re-regulation after sealing.

CONSTITUTION: A shaft fitting insertion hole 7 is provided vertically in the fixing part 13 of an engine, and a restriction shaft 1 is fit-inserted in the shaft fit-insertion hole 7. A striking hole 8 is provided horizontally toward the shaft fit-insertion hole 7. The restriction shaft 1 consists of a hard part 11 and a soft part 10, and fixing key 25 is constituted strikably on the restriction shaft 1 through a striking hole 8. The key is struck, and an engaging recessed part 27 is engaged on the soft part 10 of the restriction shaft 1 so as to engage the abutting part 26 of the key 25. Thus, rotation at movement of the restriction shaft 1 becomes impossible by engagement of the key 25 so as to prevent certainly altering operation after engine shipment. When the soft part 10 of the restriction shaft 1 is cut out after sealing, re-regulation of the restriction shaft 1 can be carried out easily.