The kart should be fine. All of our karts have been stored over the winter in my garage. It is an attached garage, but it sill gets very cold here in Chicago. Come spring, check the brakes before hitting the track. Occasionally, I dismount the tires. Have had the moisture in the tire sometimes cause corrosion of the rims.
For the engine, I add Mavel Mistery oil through the spark plug hole to coat the cylinder wall. Come spring, rebuild the carb. If you have a water cooled engine, either keep indoors or drain every once of water out of it.
LAD Specialties customer / tony kart / rotax / kt100