Air-cooled internal combustion engine

An air-cooled internal combustion engine which comprises a crankcase which defines an inner space and an outer space, said crankcase including at least one opening therein which communicates between the inner space and the outer space;

• a cylinder barrel fitted in each opening to extend from the inner space to the outer space, each cylinder barrel including a first external threaded portion located along the length thereof in the region of the associated opening and a second external threaded portion located along the length thereof in the outer space;
• a bearing ring positioned between each cylinder barrel and the associated opening in which it fits, each bearing ring extending from the inner space to the outer space and including a flange portion located in the inner space which is abuttable against the portion of the crankcase forming the associated opening, an internal threaded portion which is cooperable with at least said first external threaded portion of the associated cylinder barrel, and an outer threaded portion located on a portion thereof which is in the outer space;
• a ring nut screwed on said outer threaded portion of each bearing ring to brace the bearing ring to the portion of the crankcase forming the associated opening;
• and a lock nut screwed on said second external threaded portion of each cylinder barrel to brace the cylinder barrel to the associated bearing ring.