• A lot of Yamaha two-strokes with 250cc engines are dirt bikes.Compassionate Eye Foundation/Digital Vision/Getty Images
  
  Most contemporary motorcycles use a four-stroke engine, which means that the pistons take four strokes to complete an engine cycle. There are few two-stroke engined bikes around, but Yamaha still makes one with a 250cc engine, the YZ250 enduro motocross bike. Yamaha also has an array of older bikes with two-stroke engines of about 250cc.
  
  

YZ250

• The most recent Yamaha 250 two-stroke, offered for 2011, is the YZ250. The bike has won supercross races and is one of very few two-stroke motorcycles available new.
  
  This dirt-bike has a 249 cubic centimeter engine (volume refers to the volume inside the cylinders that is swept by the pistons). The bike has a light aluminum frame and weighs just 227 lbs. fully loaded. It comes in Yamaha colors (blue and white). According to Yamaha, two-strokes are also cheaper to maintain than four-stroke bikes.
  
  The YZ250 has a chain final drive system, which means a chain powered by the engine turns the rear wheel, and the bike has five manual gears. Both the bike's front and rear brakes are discs. A disc brake is a metal disc fixed to the wheel. When pads push on the disc, the wheel is slowed through friction.
  
  

Older Dirt Bikes

• The Yamaha IT250 was available in the 1980s and was an enduro bike with 247cc of displacement. The bike had a single cylinder, six-speed gearbox, and a chain final drive system. The DT250 was a 1970s enduro and had 246cc of displacement with a single cylinder, chain final drive system and a five-speed gearbox. Both bikes had drum brakes, front and rear. A drum brake is an internal expanding brake that slows the wheel.
  
  

Sports

• The TZ250 is a small sports bike manufactured in the early 2000s and has 249cc of displacement with a V-twin engine. The V-twin configuration means that the two cylinders are arranged at an angle to each other. The TZ250 has a front dual disc brake and a single disc rear brake.
  
  

Touring

• The RD250 was a touring-style bike built in the 1980s and had a 250cc engine with two cylinders and a chain final drive system.
  
  The TDR250 was manufactured in the early 1990s and straddled the enduro and touring groups with its high seat and enduro style suspension. The bike had a 250cc engine displacement and two cylinders. It had disc brakes on the front and rear wheels and a chain final drive system with six manual gears.