In an internal combustion engine, first and second rotating members, one for the intake valve and one for the exhaust valve rotate next to the outside of an engine cylinder on opposite sides thereof when driven by a drive gear attached to the end of the engine's crankshaft. Each rotating member may include a ring gear having a valve port or aperture near its perimeter that cyclically aligns with a corresponding valve port formed through the cylinder wall near the top of the cylinder. A method of controlling valve timing comprises the steps of causing the rotating member containing the second valve port to periodically align in synchronism with the first port to control the passage of an air/fuel mixture and exhaust gases through the combustion cycles of the engine.

Methods and systems are provided for a cam drive system of an engine. In one example, a front end of an engine includes an idler gear assembly including an idler gear and idler pulley, the idler gear in meshing engagement with a first end of a crankshaft and the idler pulley coupled to and sharing a rotational axis with the idler gear. The front end of the engine may further include first and second camshaft pulleys positioned vertically above the idler gear assembly and a cam drive belt contacting each of the first and second camshaft pulleys and the idler pulley.

A closing fork and open spring bias of a center power valve for a hitless control of an adjustable exhaust port 2-stroke motorcycle engine includes a closing fork which includes a flat plate that extends into two substantially parallel flat closing fork arms. An internal closing fork base section cylindrical wall accepts a shaft inserted there through. Each torsion spring of two torsion springs has a first extended leg including an approximately 90-degree bend about where the first extended leg extends out from a spring body of each torsion spring and a second leg extending straight out of a body of each torsion spring. Each of the torsion springs is a mirror of each other where the first extended leg extends from a different side. An upgrade kit and a method to convert a power valve system 2-stroke motorcycle engine to a hitless operation are also described.

A closing fork and open spring bias of a center power valve for a hitless control of an adjustable exhaust port 2-stroke motorcycle engine includes a closing fork which includes a flat plate that extends into two substantially parallel flat closing fork arms. An internal closing fork base section cylindrical wall accepts a shaft inserted there through. Each torsion spring of two torsion springs has a first extended leg including an approximately 90-degree bend about where the first extended leg extends out from a spring body of each torsion spring and a second leg extending straight out of a body of each torsion spring. Each of the torsion springs is a mirror of each other where the first extended leg extends from a different side. An upgrade kit and a method to convert a power valve system 2-stroke motorcycle engine to a hitless operation are also described.

An internal combustion engine is provided with a DOHC-type valve train in a cylinder head. The valve train includes an intake side camshaft with an intake side driven gear, and an exhaust side camshaft with an exhaust side driven gear. The cylinder head supports therein a spindle with an idle gear with an idle chain sprocket fixed thereto. The idle gear is in meshing engagement with both the intake and exhaust side driven gears. Rotary power of a crankshaft is transmitted via a cam chain to the idle gear to rotate both the intake and exhaust side camshafts. These camshafts are supported by bearings of a bearing wall and a camshaft holder. These bearings and camshaft holder are located, for compact arrangement, at a position axially coinciding or overlapping with the idle chain sprocket.

The present disclosure provides a sprocket structure of an engine including a crank sprocket provided in a cylinder block of an engine and driven by a crank shaft, a high pressure pump sprocket configured to receive rotational force from the crank sprocket through a timing belt, and a cam sprocket having an interior installed on a camshaft and an exterior rotatably coupled to the timing belt so as to be driven. Since a tensioner is fixed in a state in which tension is applied to the timing belt through jigs of the crank sprocket and the high pressure pump sprocket and the cam sprocket having a dual-structure, loss of tension is reduced, thus minimizing occurrence of an error of the timing belt to enhance quality of a product.

The present disclosure provides a sprocket structure of an engine including a crank sprocket provided in a cylinder block of an engine and driven by a crank shaft, a high pressure pump sprocket configured to receive rotational force from the crank sprocket through a timing belt, and a cam sprocket having an interior installed on a camshaft and an exterior rotatably coupled to the timing belt so as to be driven. Since a tensioner is fixed in a state in which tension is applied to the timing belt through jigs of the crank sprocket and the high pressure pump sprocket and the cam sprocket having a dual-structure, loss of tension is reduced, thus minimizing occurrence of an error of the timing belt to enhance quality of a product.

A chain cover is configured to cover a timing chain that transmits rotation of a crankshaft of an internal combustion engine to a camshaft. The chain cover includes a crankshaft-side opening forming portion that defines a crankshaft-side opening into which the crankshaft is inserted, and a general portion that is a section different from the crankshaft-side opening forming portion. The crankshaft-side opening forming portion is made of a first material. The general portion is made of a second material. The first material and the second material are different from each other.

In an aspect, a tensioner for an endless drive member, comprising a shaft and base that are mountable to be stationary relative to an engine, a tensioner arm that is pivotable relative to the shaft about a tensioner arm axis, a pulley on the tensioner arm rotatable about a pulley axis that is offset from the tensioner arm axis, and that is engageable with an endless drive member, a bushing that is positioned radially between the pulley and the tensioner arm to support the pulley radially during relative rotation between the pulley and the tensioner arm, a tensioner spring that is positioned to urge the tensioner arm towards a free arm position, a damping element that engages the tensioner arm and that is engaged by a plurality of axially spaced segments of the tensioner spring.

In an aspect, a tensioner for an endless drive member, comprising a shaft and base that are mountable to be stationary relative to an engine, a tensioner arm that is pivotable relative to the shaft about a tensioner arm axis, a pulley on the tensioner arm rotatable about a pulley axis that is offset from the tensioner arm axis, and that is engageable with an endless drive member, a bushing that is positioned radially between the pulley and the tensioner arm to support the pulley radially during relative rotation between the pulley and the tensioner arm, a tensioner spring that is positioned to urge the tensioner arm towards a free arm position, a damping element that engages the tensioner arm and that is engaged by a plurality of axially spaced segments of the tensioner spring.