Re: Transporting a motor bicycle - on its side...
what we all need is a fuel tank from a small outboard motor,designed to be transported on their side,with a closeable vent on the tank cap.as well the cap needs to seal really well.as well as shutting off fuel and running it out of gas.
four stroke engines will tolerate being tipped on one side or the other,usually carb/intake side will flood cylinder with oil and will be nasty to start.
would have to experiment to see what side gives the least trouble or leaves the smallest mess.
hitch mounted bike carrier is all i have to say about that....