Abstract: A four-stroke cycle engine unit for a working machine, for example, generally a valve drive mechanism for driving the exhaust and intake valves. The valve drive mechanism comprises a crank cam assembly mounted to a crank shaft of the engine unit so as to be rotated in accordance with rotation of the crank shaft, a cam gear assembly mounted on the cam shaft and meshed with the crank cam assembly, a cam assembly mounted onto the cam gear assembly so as to be rotated in accordance with rotation of the cam gear assembly, a pair of first and second lifters mounted on a lifter axis portion positioned in parallel to the crank shaft, the lifters being rocked in accordance with rotation of the cam assembly, a pair of first and second push rods lifted up and lowered in accordance with rocking motions of the first and second lifters, respectively, and a pair of first and second rocker arms operated in association with the first and second push rods.

Abstract: A four-stroke cycle engine particularly for a working machine including a crank chamber structure comprises a crank chamber body defining a crank chamber in which a lubrication oil is sealed and in which a crank shaft mounting a counter-weight member thereon is rotatably supported, a rib member provided for the crank chamber body projecting in the crank chamber near the counter-weight member and a cover member for covering the crank chamber body. The cover member is provided with a projecting portion substantially facing a side surface of the counter-weight member and projecting deeply inside the crank chamber.

Abstract: A four-stroke cycle engine unit for a working machine has generally a lubricating device for lubricating mechanical parts in a valve chamber and a cam chamber. The lubricating device comprises a body which has the cam chamber and a crank chamber, a cylinder head and a head cover having the valve chamber, and a mechanism for preventing a lubricating oil from escaping from at least one of through holes for push rods provided in a wall of the valve chamber and the cam chamber.

Abstract: A four-stroke cycle engine unit for a working machine has generally a lubricating device for lubricating mechanical parts in a valve chamber and a cam chamber. The lubricating device comprises a body which has the cam chamber and a crank chamber, a cylinder head and a head cover having the valve chamber, and a mechanism for preventing a lubricating oil from escaping from at least one of through holes for push rods provided in a wall of the valve chamber and the cam chamber.