Abstract: An internal combustion engine including an engine housing having a cam chamber and an aperture providing access to the cam chamber. The engine also includes an insert at least partially made from plastic received within the aperture, a crankshaft coupled to the engine housing for rotation about a crank axis, and a cam shaft defining a cam shaft axis and at least partially made from plastic that is rotatably driven by the crankshaft. The cam shaft includes first and second ends and at least one cam lobe positioned between the ends. The first end is rotatably supported by the engine housing and the second end is rotatably supported by the insert. The engine also includes a metal portion coupled to either the insert or the cam shaft. The metal portion defines a flange having a face in contact with an adjacent surface of the other of the insert and the cam shaft.

Abstract: In one embodiment, the invention provides an internal combustion engine including an engine housing having a crankcase defining a crank chamber adapted to contain a lubricant. The engine also includes a crankshaft coupled to the engine housing for rotation about a crank axis, the crankshaft disposed within the crank chamber, and a counterweight disposed on the crankshaft for rotation with the crankshaft about the crank axis. The engine further includes a splasher disposed on the crankshaft for rotation with the crankshaft about the crank axis. The splasher is adapted to direct the lubricant in a radial direction away from the crank axis and in an axial direction substantially parallel to the crank axis during rotation of the crankshaft.

Abstract: A four-stroke internal combustion engine is provided that is capable of use in many power tools, including those power tools subjected to tippable applications. The engine includes an oil reservoir and a crank chamber separated by a divider. The divider includes a slot that allows lubricant to move from the oil reservoir into the crank chamber and from the crank chamber into the oil reservoir in response to pressure fluctuations of the engine. The engine can include an insert positioned within the slot to at least partially restrict the slot thereby modifying the lubricant communication between the crank chamber and the oil reservoir through the slot. The insert can be wedge-shaped and at least partially define a passage such that when the insert is positioned within the slot the transfer of lubricant between the crank chamber and the oil reservoir occurs through the passage.