Re: Twin Engine Rack Mount
Two 2-stroke engines, conceavably, could be arranged to drive one wheel or could be arranged to each drive its own wheel, but either arrangement would present difficulities. Since your experience is limited, start with a simpler one-engine arrangement.
Simply because you have some particular material doesn't mean it's possible to use that material.
Make a one-engin m-bike, and keep the remaining engine as a spare.
(However, if you insist on using both engines, put caged propellers on them and make a duel-prop air-propelled bike.)