Motorcycle

In a motorcycle having an exposed two-cylinder air-cooled engine, said motorcycle having a front wheel and a rear wheel, said motorcycle having a mainframe to which is a front wheel assembly with handlebars is rotatably connected and to which a rear wheel assembly is pivotally connected, the improvement comprising:

• a. a rigid, generally rectangular mainframe including
• i. a single rigid tubular backbone having a generally horizontal portion having a front end and a rear end, and a generally vertical portion having an upper end and a lower end, said rear end of said generally horizontal portion being rigidly connected to said upper end of said generally vertical portion, said generally vertical portion having a connection cylinder rigidly connected thereto near said lower end of said generally vertical portion,
• ii. a single rigid tubular downtube having an upper end and a lower end, said upper end of said downtube being rigidly connected to said front end of said generally horizontal portion of said tubular backbone,
• iii. an engine support cradle having a front end and a rear end, said front end of said engine support cradle being rigidly connected to said lower end of said downtube and said rear end of said engine support assembly being rigidly connected to said lower end of said generally vertical portion of said backbone, said engine support cradle having two hollow generally horizontal spaced-apart engine support members each of which has a front end and a rear end, the front ends of each of said two hollow generally spaced-apart engine support members being rigidly connected to said lower end of said downtube and the rear ends of each of said two hollow generally spaced-apart engine support members being rigidly connected to said lower end of said vertical portion of said backbone,
• b. a two cylinder air cooled engine rigidly connected to said engine support cradle and to said horizontal portion of said backbone, said engine having a generally horizontal drive shaft located on the left side of said engine, said horizontal drive shaft having a first sprocket connected thereto,
• c. a transmission connected to said engine and to said connection cylinder, said transmission being located adjacent to said engine and inside said mainframe, said transmission having a generally horizontal driven shaft on the left side of said engine, said generally horizontal driven shaft of said transmission being parallel to said drive shaft of said engine, said horizontal driven shaft having a second sprocket connected thereto, said horizontal driven shaft being driven by a belt rotatably connecting said first sprocket to said second sprocket, said first sprocket and said second sprocket being covered by a plate rigidly connected to said engine and said transmission and to said connection cylinder, said transmission having a drive shaft on the right side of said transmission for driving a chain connected to said rear wheel of said motorcycle, said drive shaft on the right side of said engine being covered by a plate rigidly connected to said transmission and to said connection cylinder, and
• d. a rear wheel support assembly pivotally connected to said connection cylinder, said rear wheel support assembly having two parallel swingarms, each of said swing arms having a front end and a rear end, the front ends of each of said two parallel swingarms being pivotally connected to said connection cylinder, said rear wheel being rotatably connected to each of said rear ends of said parallel swingarms.