just seen this on ebay,
eBay Australia: BR NEW 50cc Four Stroke Chopper Pocket Bike (item 330136204992, end time 23-Jun-07 14:56:03 AEST)
pitty only 50cc sure u can put in a 140cc and hide it :P
juz browsing threw the net and found this site they start at 8k usd ,, any design u want custom built video explains it self
http://www.quadkillers.com/Demo%20Videos/yellow_quad.mpg
http://www.quadkillers.com/Demo%20Videos/yellow_quad_racing.wmv...