The half moon key is called a woodruff key and idk much about how electrical karts are built but I've worked on industrial electric ac/dc motors for 17 years now and that key is just fine. And the above post was spot on. Except I would personally not use a pm (perm magnet) motor. There is to much vibration and movement on a kart. The mags could easily bust and your motor would be locked up and turn into a boat anchor. Def use golf kart and fork truck parts. I've built two gas karts now and working on my first two seater after thatim gonna build a massive electric kart that my company is gonna pay for lol. Maybe it's because I'm in the bussniess but I'm hitting up the fork truck company's I rebuild their motors for to get my controlls I would advise everyone who reads this to get online find your local fork truck service company's and call them up and ask them about getting control parts and pedals and whatever u might need they have these parts just laying around as I do the dc motors yes they mightn't used but as long as they tell u they r E OK then it's a now brainer. These parts aren't cheap online u just need to get creative and figure out who to call. Fork truck repair centers, golf coarse maintanence shops( normally located at the coarse) places like my shop which is an electric motor repair shop. They sometimes like myself have used or rebuilt dc motors and contacters. I'm just trying to help. Soundalike I'm just rambling now lol good luck guys. Any ?'s about dc motors u have don't hesitate to ask theirs not one I haven't seen lol.