Homebuilt airplane?

I want to know the possibility of making an airplane out of a dirtbike engine. I was thinking a 650 4 stroke. I would like it to be light as possible and be able to carry 2 poeple and a bag or two. any idea how fast this would go and if i could take it off and land it from a field?
Update: what if i used a larger 1000cc engine from a sportbike or maybe 2 650cc's? or maybe even a vw beetle? i was just attracted to a dirbike because it has an engine, brakes, and suspention
8 answers 8