First off, how does it start now? If you just went out there and turned the key?
I keep a carbed Polaris ATV at my hunting propety in a frozen storage shed that is sometimes colder than it is outside and it fires up every time. Some machines are just good winter starters. You might not have any problem at all.
Agree with either a battery tender or a solar battery maintainer and full synthetic oil.
What about a magnetic block heater?
Are you sure your block is iron and there’s a large enough place somewhere where you can stick the heater? Lots of aluminum on these machines, I know my machine has an AL block.
As far as theft prevention, personally, I’d build or have someone build a little “storage cube” for the atv. 4 walls and roof that’s just bigger than the ATV. Look online and you’ll get the idea. This kind of “mini garage” was very common when I lived in the UK because motorcycle theft there is rampant and very few people have car garages or room in them for a motorcycle. They had these little steel slant roof sheds that were just big enough to roll a motorcycle in.
I’d also chain it up, but the biggest thing is that a perp is going to be real hesitent to go messing around to try to steal what they can’t see and therefore don’t know how hard it will be to steal or what the value is. For all they know, it could be Giggles the Clown’s clown car in that little shed. Perps want a sure thing, thye don’t want to risk it if they don’t know what they’re getting.
Grouse