I’d take a rag with WD40 and wipe down the chassis. If there is a gauge on the kart, bring just the display module indoors, along with the tires and rims if you have the space. Leave the brakes for the spring so long as the resevoir has fluid. Before you bleed them in the spring, you’ll need to find out which type of brake fluid your brake system takes plus purchasing a breeder tool which in no more the an elevated tank. Bleeding the brakes will no be a big deal, but if you’re buying a used kart and don’t have its history, consider a complete brake job. Pull the pads to check for uneven wear or excessive wear. Then think about removing the pistons from the caliper and master cylinder, checking the pistons and their bores for damage. And since you’ve gotten this far, replace all the seals. Stopping is more important than going.
As for the Yamaha, a few drops of Mystery Oil in the spark plug hole and put the plug back in. I bing my engines inside for the winter but that’s me. Your engine should fine in the garage.
Drain the fuel in the tank and put it in your weed wacker or snow blower.
LAD Specialties customer / tony kart / rotax / kt100