| MODEL | YAMAHA YB-1 FOUR 2002 |
| Year | 2002 |
| Engine Type | Single cylinder, four-stroke, SOHC, 2 valves |
| Displacement / Capacity | 49 cc / 2.99 cu in |
| Bore X Stroke | 36.0 x 48.6 mm / 1.4 x 1.9 in |
| Compression Ratio | 9.5:1 |
| Cooling System | Air |
| Max Power | 3.0 kW / 4.1 hp @ 7500 rpm |
| Max Torque | 4.0 Nm / 3.0 ft-lb @ 6000 rpm |
| Ignition | — |
| Induction | Carburettor |
| Start System | — |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 4-speed |
| Clutch | — |
| Final Drive | Chain |
| CHASSIS SPECS | |
| Frame | — |
| Front Suspension | — |
| Rear Suspension | — |
| Front Brakes | Drum (expanding) |
| Rear Brakes | Drum (expanding) |
| DIMENSION SPECS | |
| Overall Length | 1785 mm / 70.3 in |
| Overall Width | 655 mm / 25.8 in |
| Overall Height | 960 mm / 37.8 in |
| Seat Height | 745 mm / 29.3 in |
| Wheelbase | 1190 mm / 46.9 in |
| Ground Clearance | 130 mm / 5.1 in |
| Dry Weight | 83 kg / 183 lb |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | — |
| Rear Tyre | — |
| FUEL SYSTEM | |
| Fuel Capacity | 7.2 Litres / 1.90 US gal |
| Fuel Consumption | — |
| Top Speed | — |
The YB-1 Four is a basic air-cooled 50 cc four-stroke step-through moped with a four-speed gearbox, aimed at cheap everyday transport in Japan. Its simple drum brakes and large fuel tank for the class make it a no-frills commuter.
