An engine
lubrication method is provided. The four-cycle engine has a lightweight aluminum
alloy engine block having a cylindrical bore and an enclosed oil reservoir formed therein. A
crankshaft is rotatably mounted in the engine block for rotation about a
crankshaft axis. A
piston reciprocates within the bore and is connected to the
crankshaft by a connecting rod. A
cam shaft is rotatably mounted in the
crank shaft chamber for rotation about a
cam shaft axis, parallel to the
crank shaft axis. An
oil pump driven by the
cam shaft, which mates by cam gear with
crank gear that is driven by crank shaft, inhales the oil from the oil reservoir to splash lubricate into the crank shaft chamber. The engine is provided with a
cylinder head assembly defining a compact
combustion chamber having a pair of overhead intake and exhaust ports and cooperating intake and exhaust valves. A lightweight, high-powered engine is thereby provided having relatively low HC and CO emissions. A circular arc wall surrounds around web of the crankshaft with a slight distance from the web. A scroll-shaped wall has gradually increased distance from said wall to the direction of rotation of the web and has partial overlap with the circular arc wall. The
check valve splashes
breathing mist oil from crank shaft room to
breather room and causes the oil to supply to lubricate engine parts in valve chamber and the oil, after lubricating the parts, is returned into the oil reservoir.The oil in crank shaft chamber, after lubricating engine parts, is returned to oil reservoir guided by scroll-shaped wall and a hole provided on the scroll-shaped wall.In case of stock of engine oriented
power take off side up or down, oil is prevented to flow from oil reservoir to
combustion chamber by a weir which is provided between circular wall and scrolled or extended wall.