Re: Found a Sweet Engine, What Now?
I'd build or modify a frame to fit the engine. Start with a good strong frame and either add a drop loop or modify the existing space.
But also concentrate some effort toward brakes, tires, rims and spokes. That's a lot of engine for a motorized bicycle but a much better option that some of the monster, big CC things that have been suggested here before.
Good luck and keep us posted on the build.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"