Patent ID: 7013860

Claim:
A lubrication device for a dry-sump, four-stroke engine, comprising: a crankcase having a divider wall; a crank chamber and a separate chamber with the divider wall interposed in between the crank chamber and separate chamber; a crankshaft housed in the crank chamber, driven by a reciprocating movement of pistons, and having a crank web facing the divider wall, wherein the crank chamber and the separate chamber are separated by the divider wall in a direction along an axis of the crankshaft; a through hole formed in the divider wall for connecting the crank chamber with the separate chamber, and opened by the crank web when the piston moves from a top dead center position toward a bottom dead center position, and closed by the crank web when the piston moves from the bottom dead center toward the top dead center position; a return hole connecting the crank chamber and the separate chamber, for returning lubricant oil that flowed by way of the through hole into the separate chamber from the crank chamber, back to the crank chamber by utilizing pressure fluctuations within the crank chamber; and an oil pump that auctions up the lubricant oil from a bottom region of the crank chamber.