Underbone
The underbone engine is positioned between the rider's feet but the rear wheel is driven by a regular motorcycle secondary chain drive.
Styling considerations only mean that the chain-driven nature of the machine tends to be concealed under sheet-metal covers to a greater extent than that of motorcycles.
In only one significant respect does the underbone differ from the conventional motorcycle - there is no frame member or fuel tank between the seat base and the headstock.
The underbone arrangement improves the ease of mounting and dismounting and contributes to the cross-gender appeal of the layout as an around-town shopping and commuter vehicle.
In other respects, the technical sophistication of underbones tended to lag those of larger motorcycles, but nowadays they are increasingly equipped with similar electronic ignition, fuel injection, etc.
Underbones may have spoked or alloy wheels that are spindle mounted and usually sized to fit small conventional motorcycle frames.
[citation needed] The spine-framed, plastic-faired Honda Super Cub is the most produced motor vehicle of all time.
[3][4] Production of the Super Cub began in 1958, surpassing 60 million units in April 2008, and continuing to be made in several countries around the world as of 2012[update].
In Indonesia, this type of bike are called "ayago" (ayam jago means rooster) Underbone motorcycles often come with storage, and this may vary between markets.
The market for underbone motorcycles is dominated by Japanese manufacturers, though many of them are built in factories elsewhere, including China and Taiwan.
Many enthusiasts modify their underbones either for a show (such as installing small sound systems, neon lights and custom paint jobs) or for performance (like increasing the engine power and fine-tuning the suspension).
In Singapore and Malaysia, it is not uncommon to see old bicycles customized with parts found on an underbone motorcycle, a growing trend popular with the youth.
One of the most popular categories is the 150cc four-stroke fuel-injected class and may have engine power output ranging from 24 to 32 horsepower and can reach up to 180 km/h.
