A lubricating composition comprises an oil-soluble poly(2-oxazoline) additive having the repeat unit:

—N(COR.sup.1)CH.sub.2CH.sub.2— where the number of repeat units (n) is an integer between 4 and 1000; where the polymer carries an inorganic or organic nucleophilic polymerization terminating group t, and a linear, branched or cyclic hydrocarbyl polymerization initiator group (i); and where R.sup.1 comprises a single or a mixture of linear branched or cyclic hydrocarbyl groups having 1-100 carbon atoms, some or all having 12-100 carbon atoms, or of at least one macro-monomeric hydrocarbyl group with more than 50 carbon atoms provided that when the polymer is a homopolymer and R.sup.1 lacks any hetero atoms; (A) i has a molecular weight of less than 250 g/mol, and R.sup.1 has an average number of carbon atoms of 12 to 50; or (B) n is greater than 15.

The polymer may provide the composition, in the form of a lubricant, with friction modifier, and with low impact on lubricant viscosity.

The polymer may be a homopolymer, a block copolymer or a star polymer.

A breather chamber for an internal combustion engine wherein the breather chamber has a large size that is formed while an increase in the size of the internal combustion engine is suppressed. The breather chamber of an internal combustion engine includes looped cam chains for transmitting the power of a horizontally disposed crankshaft to camshafts provided in cylinder heads and includes cam chain chambers disposed alongside portions of cylinder block portions which intersect the direction of the crankshaft. The breather chamber is located on a side of a plane formed by a rotation locus of the cam chain in the direction of the crankshaft in the cam chain chamber.

Embodiments are directed toward an engine. In some embodiments, the engine includes a water pump and a balancer shaft. In some embodiments, the water pump has a plain bearing. In some embodiments, plain bearing is supplied with pressurized oil. In some embodiments, the balancer shaft drives the water pump as well as cam shafts.

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.

An engine includes a cylinder, a rocker chamber, an air filter, a crankcase and a rocker chamber cover, wherein the rocker chamber cover is disposed above the cylinder. The engine further includes a cover plate, wherein the cover plate is located at the top of the rocker chamber cover, and the rocker chamber cover and the cover plate are spliced to form a separation cavity and a connection channel. According to the engine provided by the invention, the top structure of the rocker chamber is re-designed and the top space of the rocker chamber is sufficiently used so as to achieve the objects of optimizing a lubricating system and reducing emission, as well as reducing the manufacturing cost and difficulty.

A seal structure for an internal combustion engine comprising: a cover side seal member which extends on upper surface sides or lower surface sides of both of an engine main body section and a chain casing and pressed and held against a cover member; a casing side seal member arranged at left or right end section of one end surfaces of the engine main body section onto which the chain casing is attached and pressed and held against the chain casing; a receiving concavity formed to extend on a junction surface of the chain casing to the cover member; and an extremely thick connection block section formed integrally on one end section of the casing side seal member, fitted into and retained by the receiving concavity, and projected more toward the cover member side than a junction surface of the chain casing to the cover member in a free state.

An internal combustion engine provided with a cylinder block which can move relative to a crankcase is provided with a block movement mechanism arranged at just one side of the left and right of the internal combustion engine, a support member supporting a side surface of the cylinder block, and a pushing member pushing against a side surface of the cylinder block at the opposite side to the side surface supported by the support member. Further, the support member supports the side surface of the cylinder block at the side of arrangement of the block movement mechanism, while the pushing member pushes against the side surface of the cylinder block at the opposite side to the side of arrangement of the block movement mechanism.

A case that houses a chain includes a first cover member fixed to a cylinder block and a cylinder head, and a second cover member arranged on the opposite side of the cylinder block and the cylinder head from the first cover member. In an intermediate part, which is a part of a confronting wall of the first cover member between the first flange and the second flange, a cover-side rib is provided, having a height so that a distal end of the cover-side rib is not in contact with the cylinder block.

An engine having a cylinder fastened to the engine ease with the biconcave internal partition, which divides the cylinder into the upper and bottom parts. Sparking plugs are mounted on both sides of the partition. The upper and the bottom parts of the cylinder have side scavenging channels which connect suction spaces to the working spaces of both parts of the cylinder. The upper and bottom parts of the cylinder have inlet and outlet orifices. Inside the upper and inside the bottom part of the cylinder and the upper and bottom piston are placed respectively, while both pistons are directed towards each other by the working surfaces. The pistons are connected by a rod that is led through the linear bearing that is embedded in the partition forming a seal. The connecting rod is fastened to the bottom piston and by its other end it is connected to the crankshaft.

An engine-driven working machine capable of suppressing vibration, and further securing output power of an engine is provided. An engine-driven working machine 10 is a generator in which an outer case 12 is formed to be substantially rectangular in plan view that extends in a longitudinal direction, and an engine 15 is housed in an inside 13 of the outer case 12. In the generator 10, a crankshaft 41 is disposed to intersect the longitudinal direction of the outer case 12. Further, an intake port 44 and an exhaust port 45 are disposed in the longitudinal direction of the outer case 12. Furthermore, a carburetor 61 is disposed at a side of the intake port 44, and a muffler 67 is disposed at a side of the exhaust port 45.