Underbones are usually built around a singular tube frame (the "underbone") that supports the wholeMost underbones are still using carburetors for the fuel system, with the exception of Honda Wave 125i which uses fuel injection. 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. Underbones usually carry engines of about 50 cc to 125 cc with the largest displacement being 150 cc for bikes such as the Suzuki Raider 150. Most modern underbone models are capable of reaching highway speeds (at least 110-120 km/h) and allowed to be used on expressways in Malaysia, Singapore and Thailand. However, underbones are not allowed to be used on Indonesian tollways and Philippine tollways.
Underbone accessoriesMost underbone motorcycles sold in Southeast Asia comes with standard steel basket, allowing riders to carry goods. For more storage capacity, riders can also purchase optional removable storage compartment (also known as the top box), which comes with free installation of the bracket to the frame to attach the storage compartment. Some underbone models such as Honda Wave and Modenas X-cite comes with additional storage compartment under the seat (motorcycle trunk) for more storage capacity.
Underbones developed from early moped models introduced in the early 1950's, many of which were simply bicycles with motors attached. One of the first underbone like motorcycles was the Honda Cub and it was arguably the success of the Cub that brought about the modern underbone. However, it was later plastic bodied, tube frame mopeds like the Honda Wave that set the modern standards from which most, if not all underbones are drawn from today.
The origin of the word "kapchai"
The word "kapcai" or "kapchai" is originally a slang derived from Malaysian Cantonese and Hokkien, its origin is from the word Honda Cub. In Cantonese "Cai" means "little" or "Son". Therefore,"Kapcai" literally means a "Small Cub". Honda is a popular brand in Malaysia and as a result of this, all underbone motorbikes were called "kapchai".
In South East Asia, underbones are very popular. There exists a healthy market for aftermarket and tuner parts. Many enthusiasts modify their underbones either for show, such as installing small sound systems, neon lights and custom paint jobs or for racing, like increasing the engine power and fine tuning the suspension. Illegal underbone drag racing has become popular in countries like the Philippines, this poses a problem as underbones offer little protection in the event of a crash. The most popular underbone for these purposes is the Honda xrm although similar models from Kawasaki and Yamaha are also frequently used. Street racing culture among teenage underbone riders in Malaysia has now become serious, especially in large urban areas such as in Kuala Lumpur, Penang and Johor Bahru. The street racers who are known as Mat Rempit always ride in dangerous manner and they are famous with their Superman stunt and also their cilok antics where they weave in-between the moving traffic at high speed. The Malaysian Police and Road Transport Department frequently launch operations to curb street racing.
Basically, the market for underbone motorcycles are mostly dominated by Japanese manufacturers. However, Chinese and Taiwanese manufacturers also produce their underbone models, but most models are copied directly from the existing models by Japanese manufacturers, which is considered as copyright violation issue. Some of the mostly copied models include Honda Wave series and Yamaha Lagenda series. MZ Motorrad of Germany is currently the only non-Asian underbone manufacturer; however, their underbone models are not produced in Germany but rather in Malaysia.
The major underbone manufacturers are as follows:-