Underbones or Underbone Motorcycles are a class of small motorcycles based on a singular tube frame, the 'underbone' supporting the vehicle. Underbone cycles fall somewhere between scooters and motorcycles, and are called mopeds in Western countries when also fitted with pedals.
This underbone cycle is popular in East Asian and South East Asian countries for their low cost, handling performance, reliability and fuel efficiency. In Malaysia or Singapore this vehicle commonly known as Kapcai or Kapchai, while in Indonesia, it is called “motor bebek”; in Thailand they called Mocyc.
Most underbones use carburetors for the fuel system, while most motorcycles have their fuel tanks positioned at the top front part, the fuel tanks in underbones are located below the seats. All modern underbones use capacitor discharge ignition for the ignition system. Tiger Underbone motorcycles carry engines ranging from 110 cc to 135 cc.
Most modern underbone models are capable of reaching highway speeds (at least 110-120 km/h) and are in some countries allowed to be used on expressways in Malaysia and Singapore, underbones are not allowed to be used on Indonesian, Philippine, and Thai tollways.
Underbones developed from early moped models introduced in the early 1950s, many of which were simply bicycles with motors attached.
