PURPOSE: To prevent the alteration of a fuel limiter bolt by integrating a threaded coupling section faced to the bolt and a nut operation section on the external side thereof respectively with a lock nut via a fixing layer, and causing the nut operation section to be separated from the threaded coupling section, when tightening torque is exceeded.

CONSTITUTION: A lock nut 5 is screwed to the limiting operation section 2 of a fuel limiter bolt 1 near the upper end thereof and, then, the bolt 1 is positioned and fixed. A threaded coupling section 6 faced to the bolt 1 and a nut operation section 7 on the external side thereof are integrated with the lock nut 5 via a fixing layer 8. In this case, constitution is so made that when torque acting on the lock nut 5 exceeds tightening torque, the nut operation section 7 can be detached from the threaded coupling section 6. According to this construction, when the torque acting on the lock nut 5 exceeds the tightening torque, the fixing layer 8 is broken, and the bolt 1 is locked with the threaded coupling section 6. In addition, the nut operation section 7 is separated and the coupling section 6 cannot be turned with a tool for daily use. Thus, the alteration of the limiter bolt 1 can be properly prevented.