you serious, whats wrong with the pull start, if you want a new engine just for a electric start i dont think you fully understand karts or your just rolling in money. Add a gear to your flywheel, buy a starter motor and all the needed electrics and off you go...kind of stupid....yes...although you can add a key switch so that you turn the key and then you must pull the cord and hopefully it starts if you wired it right.
honestly mate if you didnt get it, the money spent on getting an electric start on your engine would not be money well spent.
but if your engine already had a stater motor then its a totally different story, got a pic of your engine