I am a snowmobiler, so parking things for seasons is the nor, just the opposite, 30+ yrs of this!
wash, clean atv, DON"T use ethanol fuel period all yr, unless you use it all up fast
iuf you use ethanol fuel at all, I would maybe even suggest draining tank
and RE Filling with 100% NON ethanol fuel, and even add some stabilizer to it(make sure its for NON ethanol fuel)
run carb/'s dry but shutting off fuel peacock if you have one, if EFI< no worries!
, you can pull spark plug and spray some WD 40 down it
many folks like to drain oil and fill with new oil too, this way any crap won't settle and cling to the bottom of the motor when parked for a linger period!
and then many like to re change oil again in spring time, so you an drain and use CHEAP oil for winter storage if you wanted, or just drain, refill with GOOD oil, and be good to go come spring time!
if your a little more anal, you can lift atv up off ground by frame to take pressure and sag out of tires, so don't get flat spots(filling with a bunch of extra air can work too, but not TOO Much
I suggest putting a plug in your exhaust(FMF makes them they also come in handy when washing things too)
after this, you can pull battery or place it on a battery tender
if not putting on a tender, I suggest pulling battery and bringing in doors to a heated area, will last longer, and hold charge better!
also there is nothing wrong with doing almost NOTHING to your atv, MINUS fill with NON ethanol fuel
and just once or twice a month, start it up, make sure it comes up to temp and then some , or ride it a little
I have done this many times on sleds, get funny looks tearing up my grass in summer time riding them LOL
tip, if you have any mice where you park ATV< plugging exhaust is a BIG deal, as is inspecting your air box before starting atv , some even block the intake tube, pending where its parked and how many of them suckers might get near it!
Placing moth balls all about atv isn;t a bad idea either if you have mice issue's
not perfect, but seems to work better than most things!
steel wool can be used to plug exhaust and intake if you don;t have a actual plug for them