PURPOSE: To facilitate the lubricant maintenance operation and enable to prevent the other parts from being soiled in operation by centralizing the disposition of the lubricant maintenance parts on one side of the engine of a riding lawn mower, etc., and disposing the governor device parts and a starting motor on the other side.

CONSTITUTION: In addition to the parts of a governor device disposed at one side part of an engine, a starting motor 32 is further provided as another part therein. On the other hand, lubricant maintenance parts such as an oil filling pipe 34, an oil drain branch pipe and an oil element container 36 are convergently provided at the other side part of the engine. Accordingly, the lubricant maintenance operation such as oil change and oil element replacement can be facilitated because of the centralized disposition of these parts. Moreover, the link mechanism that is the part of the governor device and the starting motor 32 disposed at the other side of the engine can be prevented from being soiled by possible oil leaks.