• Yahaha introduced the Pw50 dirt bike in 1981.dirt bike airborne image by MAXFX from Fotolia.com
  
  The 1981 Yamaha Pw50 is a small-scale motorbike designed for children under the age of 10 years. The bike's engine construction and technical capabilities allow it to be easily controlled by inexperienced drivers. Yamaha started producing the Pw50 in 1981, equipping the dirt bike with a two-stroke engine and finishing it with a distinct yellow and black paint job.
  
  

Size Specifications

• The 1981 Yamaha Pw50 was the manufacturer's first attempt at designing a dirt bike for youth riders. The seat is placed at a height of 19.1 inches in order to accommodate the short legs and compact bodies of younger riders. With slight modifications, the bike's pedals can be adjusted to fit the needs of slightly smaller and slightly larger riders.
  
  The rubber wheels are 10 inches in diameter, providing a low overall elevation for the bike and its rider. The wheels are fitted with large rubber teeth allowing young bikers to maintain a controlled ride over uneven terrain. The bike has an overall height of 28.1 inches, a width of 22.6 inches and a length of 49 inches.
  
  

Engine Specifications

• The '81 Pw50 comes with a 50cc engine that provides a limited amount of horsepower, appropriate for beginning riders. The engine is a two-stroke engine, popularly used on full-sized dirt bikes because of its overall efficiency. The less-popular four-stroke engine requires four shifts of an engine's pistons, requiring more operational energy.
  
  The '81 Pw50's 50cc engine uses a simple reed-valve induction system that controls the overall speed and torque of the vehicle. The reed valve opens and closes the pathway for air and fuel to enter the bike's engine. It is a handy valve that keeps the engine operating at a consistent level. Reed valves can be replaced and upgraded in order to keep the engine operating at a high level.
  
  

Other Specifications

• Transmissions on standard dirt bikes can come in both manual and automatic varieties. The 1981 Yamaha Pw50 comes with an automatic transmission that greatly reduces the overall complexity of operating the vehicle for inexperienced drivers. Shifting gears can be a complex and often difficult skill for riders to properly master.
  
  The throttle is adjustable, so adults can monitor and shift the speed limit of the bike depending upon a child's skill level. As drivers become more proficient in the use of a Pw50, it is easy to take apart the throttle and reconfigure it to achieve a higher overall speed and acceleration.
  
  The exhaust pipe has a built-in restrictor that reduces the overall horsepower of the vehicle. If more speed is desired, the restrictor can be removed from the inside of the exhaust pipe.