X2 on Paulies idea. Its the most practical method for kart set ups. Last one i did i used a honda 13 hp horizontal shaft electric start motor with a comet sno mo clutch. Soon after i built it i flipped the crazy fast thing over and sold it. I had plenty of room for the battery for the electric start and it was a fairly simple build compared to trying to fit a motorcycle or quad motor.
I agree with mmajay. This is the way I would go for a Kart project.
I fix these small engines for a living will I'll say from firsthand experience that they are plenty powerful for a go-kart.
You don't need a 600cc streetbike engine behind you.
Get a good used Honda, Honda clone (cheaper), Kawasaki, or Briggs and Stratton engine for the project. Avoid Tecumseh engines. They are known for throwing rods, even in 100% stock configuration.
Most of the Kohler and Onan engines out there are too heavy to work well on a Kart.
That said, if you can score a good deal on a Kohler Command V-twin or a Briggs and Stratton Vanguard V-twin, it will make that gokart come alive.
You can get almost any of these engines, in good running shape, for around $ 200.00 with some looking around.
Most of these engines are offered with electic start right from the factory.
Also, they have ducted cooling systems. Which means you can shoehorn the engine into a Kart frame and let it run for hours without even moving the vehicle. It won't overheat. The flywheel fan keeps things cool. Try that on a dirtbike/streetbike engine and see what happens!
Like mmajay suggested, grab a Comet CV drive off a snowmobile and stick it on the engine. They will bolt right up.
My .02. Good luck whichever way you go!
