An underbone(or “cub”, from Honda Cub) is a type of two-wheeler motorcycle without frame components or fuel tanks between the seat base and the head of the vehicle. In short, an underbone is a cross-riding motorcycle without a “big beam”, designed for the convenience of a special group of people to get on and off, but it’s different from scooters. The underbone motorcycles use a structural tube frame covered with plastic or non-structural body panels.

Generally, the underbone fuel tank is located under the seat. The engine is located between the rider’s feet, but the rear wheel is driven by a conventional motorcycle secondary chain drive. The chain drive characteristics of the underbone are often more hidden under metal plate covers. The engine displacement of a typical underbone motorcycle is generally between 50 cc and up to about 150 cc, such as the Kamax Cub Pro 125, and Honda Cub 110, but larger engine displacements are also available.

From the way of riding, we can divide motorcycles into three types: cross-riding motorcycles, underbone motorcycles, and scooter motorcycles. In terms of details, underbones combine the advantages of cross-riding motorcycles and scooters, achieving automatic separation, stepped gearbox, and chain drive in their powertrain.

Underbone motorcycles generally use horizontally mounted single-cylinder air-cooled engines, which are compact in appearance and very light in weight, but their internal structure is completely different from scooters. underbone uses a design with a long connecting rod and a small piston. The advantage of this design is that at the same displacement, its speed will be lower, coupled with the automatic dual-clutch and stepped gearbox, it will have a fuel consumption of about 1.5 liters per 100 kilometers.

Historically, underbone motorcycles can be traced back to the early 1950s in Europe and Japan, and to the 1980s in China. Honda Super Cub began in 1958, also called as Cub motorcycle, and more than 100 million units have been sold up to now. As Honda’s global model, it has won wide acclaim for its superb technology and stable performance and is one of the most popular underbone motorcycles in the world. After decades of development, there are now several famous underbone motorcycle manufacturers for users to choose from, such as Honda, Yamaha, Suzuki, Kawasaki in Japan, Zongshen, Lifan, Kamax in China, TVS Motors in India, and Modenas in Malaysia.

Today’s underbone motorcycles are not just for commuting. To cater to the needs of users, major underbone manufacturers have developed retro, sporty, or personalized product tones. The prices are not only affordable but also stylish in appearance, which are popular among young people. The Cub Pro of motorcycle manufacturer Kamax from China is a good example. This Cub Pro has appeared in major tourist spots and has become the first choice for young people for short-distance travel.

In the global market, underbone motorcycles are very popular in Asia, especially on crowded city or town roads. These underbones are more cost-effective than cars and are very suitable for daily commuting, city shopping, short trips, and female riders. According to statistics, half of the people in Indonesia own an underbone motorcycle or scooter motorcycles.