Hey Brent,
First of all, thanks for registering for the forum.
There are a few different variables if the bike is going to be trail worthy or not. If the 4HP engine is pretty strong, then you have a decent chance. If it has a centrifigul clutch, it's not going to be that great, going up hills.. if it has a torq-a-verter setup (you can read about these on the main page of this site) then the hills shouldnt be a problem as long as everything is running and adjusted properly.
Let me know if that helped