Abstract: In a motorcycle, a head pipe is provided with one main frame part that extends rearwardly from the head pipe and a rear frame that extends substantially downwardly from the rear of the main frame part. A pivot is pierced in a pivot support part provided to the rear frame with a swing arm being attached to the pivot so that the swing arm can be vertically swung and a rear shock absorber unit is positioned between the swing arm and the side of the body frame. The main frame is cast in an aluminum alloy and the rear frame on the upside and the downside of the pivot supporting part projects on both sides of a vehicle from the pivot supporting part to attach right and left brackets for supporting both ends of the pivot.

Abstract: To provide an intake system of a motorcycle, which is capable of attenuating intake noise efficiently, and facilitating arrangement of resonators. An air cleaner includes an air cleaner case having an element and an expansion chamber with an intake passage connected thereto. Intake ducts introduce outside air into the air cleaner case. Resonators are provided on the expansion chamber and intake ducts, respectively.

Abstract: To provide an intake system of a motorcycle, which is capable of attenuating intake noise efficiently, and facilitating arrangement of resonators. An air cleaner includes an air cleaner case having an element and an expansion chamber with an intake passage connected thereto. Intake ducts introduce outside air into the air cleaner case. Resonators are provided on the expansion chamber and intake ducts, respectively.

Abstract: In a motorcycle, a head pipe is provided with one main frame part that extends rearwardly from the head pipe and a rear frame that extends substantially downwardly from the rear of the main frame part. A pivot is pierced in a pivot support part provided to the rear frame with a swing arm being attached to the pivot so that the swing arm can be vertically swung and a rear shock absorber unit is positioned between the swing arm and the side of the body frame. The main frame is cast in an aluminum alloy and the rear frame on the upside and the downside of the pivot supporting part projects on both sides of a vehicle from the pivot supporting part to attach right and left brackets for supporting both ends of the pivot.

Abstract: A predetermined volume for a fuel tank and to make the fuel tank slim and further to provide a more suitable knee-grip. The rear end portion of the fuel tank is formed into an extension extending rearwardly behind the rear end portion of the main frame and is arranged under a seat and between left and right seat rails. The fuel tank is expanded under the seat. Accordingly, even if a predetermined volume is ensured for the fuel tank, the front portion of the fuel tank in front of the seat can be reduced in width, height, and length to make the fuel tank slim as a whole and, in particular, to make a knee-grip narrower to provide a most suitable riding position.

Abstract: A crankcase for a motorcycle is divided into an upper half and a lower half. A crankshaft, a main shaft, a counter shaft, and a pivot portion are arranged substantially on a straight line along a parting plane P of the crankcase. An eccentric cam and a pivot collar are disposed in the pivot portion, and a rear swing arm is connected to the pivot shaft. The upper half and lower half are vertically mated to each other in front of and behind the pivot portion and then vertically fastened to each other. The center of the pivot collar is offset downwardly from the parting plane P.