So you were trying to find the end of the internet and you stumbled on to the above video. Looks like a good way to pass the winter months, so just buy a snowbike kit and slap it on right?.
The companies making the kits, and most of the articles you read make it seem that simple, but is it really? The short answer is yes, and then there is a much longer more truthful answer. While you can slap on a kit and rip around the back field, to build a snowbike that truly does what you want takes a lot more work. In addition, the bike you choose to convert plays a big part in it so if you are buying new keep that in mind.
Snowbikes shine in the mountains and it steep technical terrain so it is not a stretch that people who want one also ride that style terrain in the summer. The unequivocal king of that terrain is the 300 2-stroke so for the sake of this article we will cover what is needed to convert a KTM 300. A carbureted 2-stroke is one of the biggest pains to do right so it should be a great place to start.
At the most basic level your bike needs fuel, air, and spark to run. Winter results in a few things that make getting these basic needs met a challenge. You also need to keep the engine as close to its engineered operating temperature to ensure long life and good performance.
If you have a fuel injected bike skip this section, your computer will do its best to sort this out for you.
Winter has massive temperature shifts compared to summer. Often down in the valley when you start your ride it can be well below zero and quite humid, then by the afternoon you have climbed out of the fog and it is 40+ degrees and low humidity. In addition the freedom of the snowbike allows you to gain elevation MUCH faster than you can in the summer. It is not uncommon to gain 3-4 thousand feet in a single long climb.
Because of this you will want to seriously consider purchasing a self-adjusting carburetor. These carbs take into account the density of the air and adjust accordingly. While they seem at first to be some kind of black magic, the concept is actually quite simple. Air moves around a metering rod and due to the shape of the rod creates a low pressure area. The low pressure area creates suction that pulls in fuel from the float bowl. Denser air equals a stronger low pressure area and more fuel. While it is tempting to save the money and just say you can deal with a few rejets a day, in addition to the ambient air temperatures you also have the engine carb area getting quickly cooled with snow. In the matter of a few seconds the air going into the carb can go from engine temperature warm to below freezing and back to warm. This makes it impossible to account for manually.
Extra bonus: these carbs are just as amazing in the summer which makes the cost much easier to justify.
Getting clean air that is a consistent temperature into the bike is the next thing you need to address. Following the path of air the first thing is the airbox. These tend to fill with snow to a point that they eventually choke off the air filter. It is tempting to try to keep the snow out but the simplest and best solution…. Remove it. Cutting it out and replacing the filter with a turbo style cage and prefilter is the best way to solve this problem for good. Snowmobiles have figured this out a long time ago so do what they do and keep it real simple. If you want to stay more stock and use the factory plenum you can also cut the bottom of the airbox out so that snow just falls out, and then replace your foam filter with a pre-filter over your airfilter cage. With this set up worst case you just have to whack the pre filter to clean the snow off of it. The final step if keeping that air at the ideal temperature for you engine to consume it. The best way to do this is to install a carb heater (disregard if you have a fuel injected bike). These collars mount to your carb and use the engine coolant to heat the carb body and the air inside of it. In addition if you pull in any moisture it keeps it from freezing which can plug the ports in the carb and alter the airflow.
PST Intake Kit
PST Carb Heater
In the summer your motor gets up to temperature quickly and the bikes cooling system keeps it right where it needs to be. The fact that you can ride your bike in technical terrain in 90 degree heat speaks volumes to how effective the cooling system is. So when it is -20F and your bike is in 4 feet of snow the system ends up being WAY too good at it’s job. To solve this you need a thermostat and an engine cover. The thermostat simple bypasses the radiators until the motor is up to the correct temperature. This gets the bike up to temp faster and keeps it there. The engine cover can really be made of anything, but its job is to keep as much snow off the motor as possible. These are not always needed but in really deep or cold snow they are very important. You will also want to install a temperature gauge so that you can monitor the temps.
Do your research. They are not all created equal in weight, quality, price, parts availability, customer service and more. Spend some time searching the forums and asking around. This is a major part of the build so set yourself up for success. We won’t go into details with this as there are too many variables based on what your needs are to give a clear answer.
In addition to the basics there are a few other items that are not critical but will greatly increase your enjoyment in the mountains.
Your forks are too soft. Even if you have them set for a 250lb desert racer they are still too soft. You can respring and revalve to get them how you want them or you can use an AirPro. These lets you add positive pressure through your bleeder screws and keep you from bottoming out and having massive fork dive.
It is very hard to keep your hands warm especially when you are riding hard and getting sweaty. Good gloves make a big difference but there is no replacement for heated grips. These can wire directly to the battery and are a cheap and simple way to have way more fun.
Order all the parts you need to dial in your snowbike as a package. Click the link below, choose your bike model and year and add it to the cart. We have done the homework so you can be confidant that you will have everything you need for a great winter season.
Lectron carburetor(choose 36 or 38mm HV)
PST Carb Heater
PST intake kit
Trail Tech Temperature Gauge