ATVs have finally gone mainstream enough to attract the attention of the custom chopper crowd. The Discovery Network show “American Chopper, Junior versus Senior” will feature the building of a custom quad. The episode will air at 9:00 eastern time on Monday. Paul Junior starts with a new Yamaha YFZ450 and adds his own special touch to the machine. The result is viusally stunning. It should be functional, too, with parts from Fox Shox and Bling Star thrown into the mix. Dirt Wheels is planning a feature on the machine, so stay tuned.