I'm sure all of you have seen the Razor Crazy Karts. www.youtube.com/watch?v=FrGFjAlawmg I'm in the process of gathering parts to build one powered by a Robin EC06 engine. It won't be easy, but I'll give it a try. Also it won't be a quick build because although I have it in my head how to do it, I still have a lot of engineering to do. I can get all the basic dimensions from the youtube video. I will be copying their basic design. The motor spins at least 8000 rpms, and if my calculations are correct, at 4:1 reduction and a 12'' drive wheel, that's around 60 mph. So it will need a double reduction of twice that for a speed of about 15 mph. Probably using a jack shaft, but a planetary would be sweet. The motor is about 3 hp and should pull an adult okay. It's off of a water pump that destroyed the impeller and the previous owner chose no to repair. Here's what I have acquired so far. My shopping kart casters and scooter wheels are a bit larger than the Razor's, so I'll have to lower the chassis around them. My main engineering problem is the drive assembly. Engine mounted to a plate chained to a jack shaft and then the wheel. The fork going from the axle up past the motor to a steering head on top with a small steering wheel. Then a frame member welded to the sides of the frame and going up the the steering head so the whole engine, drive wheel, jack shaft and steering wheel will pivot full circle, plus a foot throttle with a cable that has it's own pivot to turn with it. Anyway, comments and ideas are welcome.