First of all, why take a dirt bike out in the snow at all? Because... if you live in a four-season part of the world, winter is too long a time to not be riding.
Before we consider the dirt bike itself, let's look at some other snow riding considerations.
To me, the most important thing is keeping warm. If I'm not warm, I'm not having fun. Period.
You CAN get specialized dirt bike or motocross gear for riding in the snow, but it WILL cost you. On the other hand, a good set of thermal underwear (pants and top) and layered clothing can keep you just as warm for a lot less. If you have an old snowmobile suit, or insulated overalls/coveralls, that can work as well. I say “old” snowmobile suit, because you run the chance of tearing or shredding it on the bike, frozen shrubs, rough ice, etc.
Overall, you're going to want enough clothing to keep you warm, but still allow movement. How much movement you need will depend on your riding style and where you're riding. An 8-foot wide track you've packed and flattened is a lot different than a snow-covered trail through the woods.
If you can afford it, an extra pair of riding boots, a size or two bigger than you need, allows room for thermal or wool socks. Depending on the specific product, you may also be able to fit battery heated socks into your regular boots. Like any winter footwear, if your toes are packed in too tight and can't wiggle a little, they're going to freeze up on you. If your riding boots have removable liners, try taking them out and wearing an extra pair or two of socks. If at all possible, the pants you're wearing (at least the outermost layer) should fit OVER your boots to keep out snow.
Body... feet... now hands. A good set of gloves is an obvious place to start. The trick is to get enough insulation without affecting your ability to work the clutch and brake. As always, temperature is a factor. Where I live we can get calm, sunny days just below the freezing point where regular riding gloves are good for a half hour or more. When it hits 40 below with a strong wind, almost nothing is going to work.
Manufacturers like MSR, Moose, and others have soft hand guards that offer increased protection, and even guards that cover your entire hand. They may not look tough, but they work. If you want to get real fancy schmancy, you can install grip heaters. Riding a dirt bike in winter is awesome, but I don't do it often enough to justify that cost.
For head gear, I still fully endorse wearing a helmet and goggles. Ice can be hard as rock. Frozen trees even harder. And the metal on your dirt bike is still there, snow or no snow, so wear a helmet. If you go to where they sell snowmobiling supplies, you can get thin head coverings (they cover everything but the face) that offer a surprisingly warm extra layer, without affecting the fit of your helmet. In addition, most of them fit well down the neck to keep any cold drafts out between your jacket collar and helmet. Full face versions are also available with eye openings, and sometimes nose and/or mouth openings. I find these collect too much moisture from breathing, which then freezes in the helmet, so I have an open face style. But I also know people who love the full-face versions – so maybe I just breathe strangely.
Goggles protect your eyes the same way they do in summer, but in winter they also keep freezing breezes out. Fogging goggles can be a problem. The easiest way to avoid fogging is to avoid sweating, because as soon as you introduce moisture into the goggles (from your skin) it'll be attracted to the cold lens. Dressing in layers helps you moderate your body temperature between riding and other activities.
You can also purchase cold-weather goggles with a built-in anti-fogging coating (don't wipe the inside of the lens if you can avoid it – you'll wear off the coating). Spray-on and wipe-on anti-fog coatings are also available, as are dual lens and even heated goggles.
One final tip. Take a bathroom break BEFORE you get all bundled up.
I'll try to get together some information on setting up your dirt bike for riding in the snow and post it soon. If you want to know about the post as soon as it hits, you can subscribe to my Twitter. If you do, I won't be telling you about my feelings or what I had for lunch... just dirt bike stuff.
Take care!
