In truth I have no idea how to store a moped for winter...cause I ain't never done so.
I don't care if it's 32 below, three feet of snow and more comin down, if I wanna ride...I'll ride, heh.
I ain't a great fan of a nice&neat appearance to my wheels, so I dun much care if salt eats the paint, neither...just sand and primer...and relube the chain and stuff, you know how that goes.
I also have a variant-style tire chains for mine...so I don't rightly care HOW much snow is out there, or slush or sleet...my lower ground pressure plus those chains...never bogged out even once, and they'll handle pack-ice too, if yer careful.
As fer cold ? I gotta snowmobile suit with an army field jacket liner underneath, ski mask and one of them lower face gizmos that makes ya look like hannibal lechter....so hell would have to freeze over afore I noticed.
You wanna find me out there this winter ? just follow that roostertail of snow flyin up....that'll be me.
(FYI, Tomos and Puch mopeds, most of em, WILL operate at up to -20....save those models which cycle the ignition via the battery circuit, and some of those might start too.)