This is a cool looking bike, and it comes with the arms/legs, so you just need your torso and heads.
via Kromlech
Legionary Breacher Bike 13,99 €
http://bitsofwar.com/home/489-legionary-breacher-bike.html
This set contains one high quality resin Legionary Breacher Bike armed with twin Thunder Guns. Designed to fit futuristic 28mm heroic scale heavy armoured troopers. As an additional parts you get biker legs and arms which you can combine with Legionaries torsos, heads, shoulder pads and backpacks sold separately.