People who see Greg Dunham's motorcycle sometimes think they've suddenly shrunk. What they're actually looking at, however, is the world's biggest motorcycle, according to the Guinness Book of World Records. Dunham built the 15-foot high, 25-foot-long monster bike in over three years. It weighs about 6,500 pounds and cost $300,000. Dunham steers it from a cage below the handlebars. The beauty shop owner said he created the monster bike because his friends said it couldn't be done and he wanted to prove it could. The reaction he gets from people who see it is icing on the cake. The Guinness Book of World Records describes the bike as the world's tallest rideable motorcycle.