Abstract: In an exhaust system for a motorcycle in which an engine main body of a multi-cylinder engine has an oil pan on a lower portion thereof, and is mounted on a vehicle body with a plurality of expansion chambers being connected to a downstream side of an assembled portion of a plurality of exhaust pipes that extend out of the respective cylinders of the engine main body, respectively. The muffler includes a first expansion chamber that is connected to the assembled portion and the other expansion chambers that are the assembled portion are disposed on one side of the oil pan. The first continuous to the first expansion chamber. The respective exhaust pipes and expansion chamber is disposed on the other side of the oil pan with the other expansion chambers being disposed to the rear of the engine main body.

Abstract: An engine cooling apparatus includes a cooling water outlet communicating with a water jacket provided in a cylinder block and a cylinder head provided on an intake port side of the cylinder head. A thermostat switches a path for cooling water discharged from the cooling water outlet, according to a cooling water temperature. A thermostat case for the thermostat is disposed downward of a line L extended from a coupling surface between a cylinder block and a cylinder head. The thermostat case and the cooling water outlet are connected via a connecting pipe. This arrangement makes it easy to secure a space for disposing the thermostat.

Abstract: An integrated power unit for a small vehicle is configured to permit a compact engine design in a power unit having a crankcase that is split into upper and lower portions. The power unit includes a crankshaft supported by the crankcase and oriented transverse to the running direction of the vehicle. A transmission shaft is rotatably supported in a transmission chamber formed on the rear side of the crank chamber. The respective split surfaces of the upper and the lower crankcase portions are provided plural fastening boss portions arranged as vertically opposed pairs. The plural fastening boss portions are respectively joined using fastening bolts to integrate the upper crankcase and the lower crankcase, thereby forming the crankcase. A clutch is disposed at one end of the transmission shaft, and the rearmost fastening boss portions overlap with a rear portion of the clutch in the front-rear direction of the vehicle.

Abstract: An integrated power unit for a small vehicle is configured to permit a compact engine design in a power unit having a crankcase that is split into upper and lower portions. The power unit includes a crankshaft supported by the crankcase and oriented transverse to the running direction of the vehicle. A transmission shaft is rotatably supported in a transmission chamber formed on the rear side of the crank chamber. The respective split surfaces of the upper and the lower crankcase portions are provided plural fastening boss portions arranged as vertically opposed pairs. The plural fastening boss portions are respectively joined using fastening bolts to integrate the upper crankcase and the lower crankcase, thereby forming the crankcase. A clutch is disposed at one end of the transmission shaft, and the rearmost fastening boss portions overlap with a rear portion of the clutch in the front-rear direction of the vehicle.

Abstract: In an exhaust system for a motorcycle in which an engine main body of a multi-cylinder engine has an oil pan on a lower portion thereof, and is mounted on a vehicle body with a plurality of expansion chambers being connected to a downstream side of an assembled portion of a plurality of exhaust pipes that extend out of the respective cylinders of the engine main body, respectively. The muffler includes a first expansion chamber that is connected to the assembled portion and the other expansion chambers that are continuous to the first expansion chamber. The respective exhaust pipes and the assembled portion are disposed on one side of the oil pan. The first expansion chamber is disposed on the other side of the oil pan with the other expansion chambers being disposed to the rear of the engine main body.

Abstract: An engine cooling apparatus includes a cooling water outlet communicating with a water jacket provided in a cylinder block and a cylinder head provided on an intake port side of the cylinder head. A thermostat switches a path for cooling water discharged from the cooling water outlet, according to a cooling water temperature. A thermostat case for the thermostat is disposed downward of a line L extended from a coupling surface between a cylinder block and a cylinder head. The thermostat case and the cooling water outlet are connected via a connecting pipe. This arrangement makes it easy to secure a space for disposing the thermostat.