Okay, I'm back near a computer, so I can respond my 2 cents worth.
As with any off-road vehicle, a complete set of spark plugs are good to carry, plus I will often carry a plug that is 1 heat range hotter just in case I start having a major fouling problem.
I carry a snatch strap, you never know when you or someone else may need a tow.
Spare tie-rod with ball joint. Also, don't forget a crows foot wrench to fit the inner tie-rod nut, what you have in your standard toolbox probably won't fit it. I think it takes a 1 1/8 inch CrowsFoot wrench, you can pick one up at a tool store (not Sears or AutoZone).
Jumper Cables, with these, you can get or give jump starts, plus with a couple of batteries, you can even weld.
Duct tape, great for all kinds of repairs. Electrical tape for patching up those wires that rub through.
JB Weld, great for fixing broken cases or fixing holes that get knocked in tanks, engine cases, diffs, etc...
Water and Antifreeze mix.
Spare Air Cleaner
Tool sets, make sure you get a realistic set, keep track of what tools you use to maintain and work on your machine, those are the same tools you need to have on the trail. Pliers, needle nose and regular ones, adjustable open end wrenches, phillips and standard screw drivers in different sizes, open end wrenchs, etc. put some time and thinking into what tools you might need.
As for AC items, most require repair in shops, so think emergency repair. Tie-rods, plugs, etc.
Axles on some models can be switched around as needed, this will depend on what model you have. But I've been known to take out a broken axle and limp back home with the 4wheel drive engaged, using the undamaged axle to pull the machine home. Usually, the front axles on the Prowlers are the ones to break, due to the angles of turning while locked in 4wheel drive. So on those, just remove the damaged axle, put it in 2 wheel drive and get home. You'll need to plug the axle where you removed it.
On the XTZs, weak spots are Tie-Rods, front ball-joint retainers, head gaskets (unless it has the new style 0830-209 gaskets), A-Arm mounts, water pumps (unless it has been updated), Diff seals (build an expansion chamber inline in the vent tubes, then run the vent lines higher usually fixes this). The air cleaner on these really have a problem of getting clogged in dusty or muddy conditions due to where the intake is. If you run an aftermarket cage, then rotate the tube that comes out of the air box to a straight up position, taking air from the passenger compartment area. It's a touch noisier, but you get cleaner air and don't clog up as much while on the trail.
Also watch your 4-wheel drive shift actuator, I've had a couple of those go out. But at worse, it will keep you in 4WD , but will still unlock the front diff. Don't run hard or on pavement and you will be able to get back home.
Also, spare drive belts are good to have along. Especially if you abuse yours running hard. But don't learn how to change the belt on the trail for the first time, try it in your garage or shop. That way you'll learn some important tricks on doing it before you put yourself in the worst conditions to change it.
For the most part, these machines are capable of handling what we throw at them, but as with any, they have some weak points that need addressing.
Lets see, have I missed anything, did I mention tie-rods...can't mention those enough, they are by far the weakest link on the entire machine, one that could leave you stranded. Those and spare sparkplugs, and tow straps are really important.
Arctic Cat Prowler Desert Race XTZ: ITP BajaCross tires on ITP Beadlocks, Beard Super TZ Seats, Crowe 5pt harnesses, King Off-Road Racing Shocks, Custom Racing Chassis with 7 inch longer wheelbase, +5 Suspension set at 16 Front and 17 inches Rear inches travel, UTVINC did the tube bending
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