Motorcycles having front and rear swing arm assemblies as the suspension members therefor are employed with lower frame structures incorporating the power unit as a structural element thereof. The lower frame structures are shown to include brackets mounted to the power unit itself, separate loop frame members and an under channel member. Upper frames are shown to be associated with the lower frames. The upper frames do not support the suspension systems but do support motorcycle equipment such a fuel tanks, air cleaners and the like.

A pair of elongated, parallel tubes. A frame is formed by transverse members joining the tubes at each end thereof. Wheels are affixed to each end of the frame and are interconnected by tie rod structures such that the wheels operate together as a steering mechanism, each wheel turning in the opposite direction of the other wheel. A cover is attached over the frame, and, together with front and rear fender members attached to the frame adjacent the ends of the frame, forms a cavity. A motor is mounted within the cavity and drives a hydraulic pump. The pump drives hydraulic motors mounted in the hubs of the wheels.

A rear suspension for motorcycles which employs primary and secondary torsion springs operating on the rotative axis of the horizontally disposed and rearwardly trailing fork carrying the powered traction wheel. The two springs are of selected resilience and are quickly replaceable without disassembly of the suspension system, and each is adjustable for controlling the normal vehicle height and pitch attitude to be subjected to varying loads. Load application to this rear suspension system is substantially central of the vehicle and with the result that radius of gyration is minimized, unsprung weight is reduced, and with improved dynamics characterized by a spring-stop snubbing action resulting in increased traction and ground engagement capability for superior handling.

A body structure for a motorcycle with a front wheel and a rear wheel, including a body frame assembly having an engine mounted thereon and having vertically swingably joined thereto a front leading arm for supporting the front wheel and a rear trailing arm for supporting the rear wheel. The front leading arm as viewed from the side thereof is curved upwardly in the direction of a steering axis of the front wheel. The body frame assembly is shaped in a concave form having front standing portions and rear standing portions to thereby surround the engine. The engine is a V-type with at least a pair of internal combustion cylinders substantially vertically arranged to be respectively forwardly and rearwardly inclined, and may be secured at a front part thereof to the front standing portions of the body frame assembly and at a rear part thereof to the rear standing portions of the body frame assembly. A shock absorber cooperation with the front leading arm and another shock absorber cooperating with the rear trailing arm are arranged under the body frame assembly which has the engine mounted thereon, to be oriented forwardly and rearwardly, respectively.

A front and rear wheel drive vehicle having straddle-type seating. A power train is located beneath the seat and between the footpegs of the vehicle. The engine employs parallel output shafts located on either side of the crankshaft to drive power transmission means to the front and rear axles. A speed change mechanism is contained within the engine case along with the output shafts and includes a first transmission shaft between the crankshaft and one of the output shafts. In one embodiment, the cylinder block of the engine is illustrated as being inclined toward the speed change transmission such that the cylinder block, cylinder head and head cover do not extend laterally outwardly beyond the engine case. To employ both output shafts, sprockets are arranged on each shaft with a coupling chain. The orientation of the output shafts provides for a narrower engine profile.