I lived in Northern Minnesota for 10 years, and during that time, I went out on my snowmobile often, in all weather, alone or in small groups of 2 to 4. My weekend trips included Upper Michigan, Northern Wisconsin, and of course Northern Minnesota forests.
Most of my trips during the year are in these same area except Minnesota.
Each trip averaged over 100 miles. As with rental sleds, my snowmobile equipment compartment was about the size of a shoebox, and unless you have the optional luggage rack, or the optional trailer hitch, most of what you carry has to go in there, or in your pockets.
Any extra gear I carry goes into a backpack. Its never really an issue for me as the weight of the pack rests on the seat while seated and the straps are basically holding the pack upright as opposed to normally having a load on them.
When renting, it is essential to check and see that the OEM toolkit is in the compartment, and that all of the tools are in there. Snowmobile trailer tip over on forest trails at normal touring speeds.
This is one of the first things I do. I also insist on actually seeing the toolkit, extra belt and spark plug for each machine. Some outfitters don't fully replace the items once used and I have had situations where they will chime out "there enough between the two machines." That doesn't fly with me - each machine in a group need to be self sufficient for servicing.
This might constitute heresy, but rather than list the equipment in my PSK, I'll tell you what I actually used in 10 years and 5000 miles of backwoods travel.
No replacement for experience- thank you.
Spare headlight bulb (hit a big bump, and they can burn out)
I think this is more of an issue on single light sleds. The newer sleds will have two bulbs for low and two for high. So I don't think this is critical but definitely worth taking a bulb along - I would probably say a low beam as a high beam can be troublesome in snowy conditions.
OEM sparkplug wrench
spare sparkplugs (sparkplugs foul often)
spare drive belt
These are a part of the sled kit. I always check for kit completeness.
magnetic compass and topo and trail maps
Leatherman Supertool (to remove barbed wire that had wrapped itself around my drive axle)and a million other things
Bic lighter (kept in my inner pocket)
Mini Maglite (also kept warm on my inner belt)
Helmet
All of these items are currently on my list. Aside from being illegal in WI and MI riding without a helmet I believe isn't a good choice.
Thin nylon balaclava (I got frostbit on my lower chin/neck crossing a frozen lake at -25. I never felt a thing. Balaclava complely eliminates this, and the thin nylon doesn't make your helmet too tight).
I cannot imagine riding without a one. I like the versions which also have a bib which lays over your pecks and shoulder blades to create a "seal" between the jacket neck and helmet.
Thin cotton gloves (for detail work that you can't wear your snomobile gloves for)
An absolute must. Gassing up without some sort of thin liner glove can be hazardous to you hand. Some of the gas pump handles in older town are metal. Ever grab a one of these metal handles at -15 or colder without skin protection? I did - once and I'll never do it again.
A retractable saw (I used to carry a small hatchet, but they are unsafe on bitter cold days when your hands are cold and ice forms on the handle during use).
Clif bars or equivalent high energy food
instant coffee and tea bags
A metal canteen cup to melt snow for beverages.
Bandana
Whistle
Extra snowmobile key in an inner pocket
I picked up a few Cliff bars for a recent trip in WI. I think out of all the health/breakfest bars I have had these are the best so far.