PURPOSE: To ensure encapsulation of a speed limiting device and to block alteration operation by a method wherein the sped limiting device rushes an inner chamber from a moving-aside chamber recessed in a support wall fronting on the inner chamber, the limit operation part of the speed limiting device is contained in the moving-aside chamber, a closing plug device is engaged with the moving-aside chamber, and a governing lever is brought into the press part of the speed limiting device.

CONSTITUTION: An inner lever 21 contained in the gear chamber 20a of an engine body is formed in such a manner that a speed is limitable by a speed limiting bolt 10. The limit operation part 11 of the speed limiting bolt 10 is moved aside to a moving-aside chamber 22 recessed in the front wall of a gear case and thereafter, the moving-aside chamber 22 is sealed with a bowl-form plug 23. Thereby, after an engine is delivered, the presence itself of the speed limiting bolt 10 can not be recognized, contact with the limit operation part 11 is impracticable to make, and alteration operation of the speed limiting bolt 10 is blocked. Thus, since the speed limiting device is shielded with combination of the moving-aside chamber and the closing plug device, it is impossible for a worker to make contact with the speed limiting device, resulting in holding a sealing state on the low speed and the high speed side during delivery.