we made most of it ourselfs we started with a 125 tkm (tony kart) race kart cut it in two just behind the seat ad extended it roughly 2 foot to take the motor we went for a gsx 600 lump as it was oil cooled not water the tricky bits are like the manifold which we modded the bike one and cables and sprockets and the fuel ( as it was gravitiy fed on the bike) now the fuel tanks between your legs we had to het a slow volume pump as for cost it depends i would want a grand for mine as it has taken alot of time and effort