Heat Exchangers: Why use them and how to setup and install.

“The ability to ride all day in any terrain and conditions without having to constantly be looking at your engine temps or adjusting rad and engine covers is truly something amazing and adds an element of fun into your days adventure.”

Why use a heat exchanger? Because radiators are not meant to be used on snow machines, and that’s why every snowmobile manufacturer uses heat exchangers- not radiators. Dirt bikes, being the fun machines they are, are made for riding everywhere except snow, and that is why you have to build them to be snow worthy. A track pushes the engine to its maximum limits, temperatures run up very quick, and having adequate cooling on demand is essential not just for engine protection but also for getting peak horsepower out of the engine.

Engines make the most power at a specific temperature range, this is something very noticeable on 2 strokes. So you have to keep it warm using an engine blanket/cover and dump the excess heat. This is where the problem with radiators shows itself:

If you blanket the engine to keep it warm all the cooling is dependent on the radiators, but you aren’t getting enough airflow through radiators for cooling on hill climbs because of slow speed WOT runs which = overheating.
If you don’t blanket engine to keep it from overheating, it will get too cold in deep powder, very cold days, side and downhill coasting, etc which = same as riding without warming up engine. These engines run on tight tolerances and need to be at a specific temperature range.
Engines running too cold without an engine blanket get the problem-causing “milky oil” you have heard about (or experienced!). This is a result of condensation forming in the oil from cold snow contacting the hot engine (like a cold glass of water on a hot day), and the engine temps not being hot enough to “boil out” the water.
Without a blanket you also risk thermal shock to cylinder and head when snow hits a hot engine, which can lead to cracking.

Benefits of a heat exchanger:

Wont ever overheat on long hard hill climbs, giving you full engine power all the way to the top.
Wont ever have issues on deep powder days with radiator guards / shrouds icing over or packing with snow and blocking airflow and overheating.
You will get steady temps all day with this kit:
- Cold engines do “fuel dumping” to bring up engine temp (an ECU controlled function). With proper engine temp, you get better gas mileage so you can go farther and ride longer.
- A common issue is overheating on the trail getting to the mountain, and then riding the mountain low on coolant all day. An engine that gets too hot may seize up and blow.
Our kit does a complete removal of the radiators so you never have to put up with covering or uncovering rads for temp control or worry about a limb blowing out your rads in those tight trees.
No more steaming rads in your face, fogging up your lens, and icing over on your gear.
A set of radiators from a KTM with a fan weigh in at just a bit over 4 pounds. The heat exchanger (ARO model) with the coolant bottle weighs in at 1 pound 14oz.
- Weight pictures: KTM rads on scale & Cooler with bottle
Add in how much snow tends to get caught up in the radiators, and as the snow melts and runs down the frame and freezes into a big chunk of ice underneath your engine, trapped in with the help of the engine blanket, the weight really starts to stack up!

This is the first and only system that does a complete removal of the radiators, and is the lightest weight and cheapest option for a system to manage all the cooling needs for your snowbike!

With the rads gone, you have more space for wiring in electrical accessories and plumbing your thermobob, heated handlebars, etc. Hose connection points are strategically placed so that it does not interfere with any gas can mounts. Our engineered design maximizes surface area for most efficient cooling in any condition and is easy to install and plumb using common 5/8” heater hose available at just about any auto parts store, and hose fittings are readily available from the hardware store. We now also stock custom hoses made just for heat exchanger conversions to minimize the amount of how fittings in your plumbing system and for a clean looking setup.

But is this the only solution for temp management on a snowbike?
No its not, there are other methods! A common method is to use coolant heated handlebars to take alot of the heat, aluminum radiator guards which act like a heat sink, a fan on the radiators to solve the airflow issue, engine blanket with removable inserts for hot/cold days, adjustable radiator blockers, and then you have a fairly reliable system. Besides the cost and all the extra weight from so many components, it still has its issues though. Sometimes its not enough cooling on the big hill climbs, so you start loosing power as temps rise and have to turn back. And what about the warm spring days when you shut off the coolant heated bars? You have to monitor engine temps and fuss around with adjusting radiator blockers and engine blankets, all that just takes away from the days fun of being able to grab a handful of throttle and go without a worry. I wanted a simple hassle free, light weight, low priced cooling setup with which I would never have to turn around on a hill climb or constantly be monitoring my temps and fussing around with covers. So I made this heat exchanger system.

“It always felt like the engine was loosing power as you climb a hill even though its not getting any steeper, and then you had to turn around or downshift. Turns out it was loosing power because it was getting too hot!”

Will it ever overheat with a heat exchanger?
For the same reason you have seen snowmobiles overheating on the trail, you may overheat. The heat exchanger will provide plenty enough cooling out in the mountain on the steep and deep full throttle. On the trail without ice scratchers– if there is not enough soft snow temps will rise. Snow needs to be getting inside the track, where it will lubricate the hyfax and get thrown on the heat exchanger. Trail may appear to have loose snow/ice- but the lugs keep the track elevated and snow it is not getting inside the track. It stays outside the track on the lugs and is thrown out the back making a nice looking roost. This is much more noticeable on the 3″ track models because the taller lugs keep the track base higher off the ground so less snow gets inside the tracks through the track windows and you have less snow for cooling and lubrication. Ice scratchers are the only way to go on hard packed icy trails! That will take care of your cooling and hyfax lubrication.

Keeping your hyfax lubricated and in excellent condition on a snowbike is more critical than you think! Consider this: You have so much weight on the track which is transferred to the hyfax whose job is to let that weight slide over the track with minimal friction. Damaged hyfax = more friction. Friction is resistance your engine must overcome to turn the track. The more friction, the more HP you are loosing just to turn the track, and us snowbikers know that every little bit of HP counts.

Ever rode a bike with a track that feels sluggish and and inconsistent stickiness at low speed? Check the hyfax. Hyfax lubrication is a very important and neglected issue with snowbikes!

Is it actually possible to destroy your hyfax that easily? Absolutely yes! Doesnt even take that long of a ride- Google: melted hyfax

How well does the heat exchanger perform on warm spring day?
Exceptionally well! Even on the packed trails it seems to cool better on the warmest spring days without an ice scratchers than on the coldest winter days with a ice scratcher. This has something to with the snow being more wet and sticky. Dry cold ice chunks don’t stick to the track and get thrown right off as the track makes a sharp turn around the rear idler wheel. Consequently the ice chunks don’t stick to the heat exchanger and just bounce off. Wet ice and snow sticks to the track and and gets thrown onto the heat exchanger, and wet snow sticks to the heat exchanger providing very good cooling.

Do I have to get the coolant bottle also to make this system work?
No you don’t. You can use one radiator to serve as coolant bottle but getting rid of the radiators completely offers several benefits.

Using one radiator as a bottle will be a bit more challenging to plumb depending on the bike model.
Each radiator weighs almost 2 pounds, and has a tendency to add ice weight wherever water trickles down and freezes.
- Coolant bottle weighs in at 0.5 pounds
It clears up a whole lot of space for running electrical accessory wires and coolant plumbing lines (heated bars, heated carb, etc.) and this extra space is really noticeable by those running BRC500 or other big bore engines.
Higher pressure radiator cap reduces chances of boiling over should you ever run into such a circumstance. My system is made to run at 2.0 bar (sea level). Although the cap does say 1.8 bar, that is only because I could not find a low priced small Japanese style (Honda, Yamaha) cap in 2.0 bar. So I machined the filler neck to put a bit more pressure on the spring, raising the boiling point to 2.0 bars.

Why do I need such a high pressure sytem? Heres a scenario: Most KTM’s come with a 1.8 bar cap giving it a boiling point of 280°F at sea level (most Honda and Yamaha have lower pressure systems). But even the 1.8 bar systems have been observed boiling over up on the hill climbs, and that’s because of the lower atmospheric pressure at high altitude making you have less than 1.8 bar. So I made this system to give you true 1.8 bar boiling point equivalent on the highest mountain tops!

Getting more scientific nerdy stuff here: Although the boiling point at 1.8 bar is around 280°F (depending on coolant mixture) during our testing the bikes observed spitting up coolant where only around 230°F and it shouldn’t have boiled at that temp even when adjusted for altitude there is still some buffer, but it is getting close. What happened is even though the system temp as a whole was below the boiling point, there was a hotspot in the coolant jacket somewhere near the head which got hot enough that it was able to boil and form bubbles, raising pressure and opening the cap valve. Air is insulating, resulting in the hotspot triggering a chain reaction and then temps spike quickly out of control just when the engine is being pushed to its maximum limits under the heaviest loads.
By raising the system pressure you provide a larger temp buffer gap between operating temp and boiling point reducing the chance of any hotspot forming.

Overflow catch can

An overflow catch can is the probably the best bang for the buck mod you can do to your bike. As coolant heats up, it expands creating pressure within the system. The excess pressure is bled out through the overflow nipple / tube onto the ground. As the system cools and coolant contracts creating a vacuum, the vacuum valve is opened allowing air to get sucked in. This air sits at the top near the cap, until you tip over or roll your bike and then the air bubble is free to go into the system and create an insulating air pocket that can cause some serious engine damage. Put the end of the overflow tube into coolant, and the vacuum will draw in coolant instead of air.

This simple coolant catch can catches expanding coolant from the overflow hose, and allows coolant to be sucked back into the system instead of air as it cools.

How to make one: DIY Coolant Catch Can
Or: Coolant catch can kit $10

Setup and Installation

This design has been extensively tested in all snow conditions with exceptional results! Keeps steady engine temps all day no matter what. To get the same results, you MUST have the proper setup! Which is:

Fully blanketed engine. You cannot have snow getting onto your engine. In addition to the engine blanket covering the front and sides, it is recommended to block off the backside so the track is not throwing snow on the back of engine. It is easily done with a piece of rubber or plastic and a few zip-ties. You want to minimize any snow from direct cooling of the engine- let the heat exchanger do all the cooling in a controlled manner.
You must have a thermobob / thermostat. Ideal temps for snowbikes are 180-195°F on a 4 stroke (around 130°F on a 2 stroke). Stock thermostats are decent, but nearly all are set to open at a much lower temp (around 160F on 4 stroke) so you may end up running under optimal temp. An aftermarket thermobob is needed for any snowbike setup.
You must understand the basic concept of coolant circuit with a thermostat and bypass, understand how your bikes OEM coolant circuit is plumbed, and understand how to plumb in a heat exchanger for your specific bike. It is actually very simple and easy, but if you get it wrong the whole system wont work.

Do your homework first! There is so many resources online and forums to help you understand this concept so you get it right the first time. Once done, we would appreciate it if you would send us pictures and / or videos of your setup so we can post it to help others figure out their setup!!

General plumbing

The 2 best methods I have found for doing the plumbing:

You can use the existing (OEM) coolant hose setup and divert the thermostat/ thermobob output to go into the heat exchanger instead of radiator, and the cold return will hook up to the radiator return line. Tap into the bypass line and divert it through the coolant bottle. This method may be easier but might end up looking messy.
Remove all OEM hoses and using bulk heater hose from an auto parts store and angled hose fittings from a hardware store you can route the hoses anywhere you want and achieve a very clean look. This gives you the most options and there is so many different ways to do it. This is further simplified by using the return hose available here: Return Hose.
1. Note: the return hose may not fit some bikes due to the header being in the way.

Go to your auto parts store and ask to browse through their rack of heater hoses. You will find all kinds of bends and angles that you can use. I prefer to use brass PEX fittings for their compact size and smooth beads make for easier disassembly than dedicated barbed hose fittings. If using PEX fittings, they are sized differently than standard fittings. For 5/8” hoses you will use 3/4” PEX fittings.

Use of plastic hose fittings is not recommended, unless they are rated for well above your engine operating temp.

Use only worm gear or screw style clamps. Do not use spring clamps – they will not hold up to the pressure. Make sure clamp is installed below the hose bead and not on the bead itself.
Having any kind of coolant temp thermometer is highly recommended to ensure your system is working properly. Install thermometer as close as possible to the hot output from the head.
- It is not recommended to install the thermometer on the bypass hose. When the bypass is closed and flow is open to heat exchanger, your thermometer may not read actual engine temp. This is model specific though, some thermostats do not fully close off the bypass.
Protect your hoses anywhere they push against a sharp corner (ARO & CMX frames mostly) the vibrations can cut through the hose. Simply cut open a piece of hose lengthwise, and wrap it:

MAKE SURE to secure hoses with plenty of zip ties so they do not bounce and contact the track!!

Here is a crude and simplified drawing of how to setup a heat exchanger:

Coolant Bottle:

Some bikes are made with the rads being the support for the side plastics, most have braces that hold plastics and rads attach to the braces, or a cage / rad guard that holds the plastics and rads fit into the cage. The coolant bottle needs to attach onto something, so if your host bike rads are the support for the plastics, you will need buy a aftermarket rad guard of some sort. Keep the radiator blockers in so there is no snow blowing into the empty side and no snow hitting the coolant bottle giving it uncontrolled cooling and opportunity for ice to collect.

Installation:

Unit is installed in place of radiator, Left or Right side – whichever side radiator had the filler neck.
Coolant bottle is thinner than stock radiator, mount it all the way forward or backward, or even diagonal to change the angle and location of filler neck to best fit your bike. (See pics in photo gallery showing some of the different mounting angles: Coolant Bottle )
You can attach aluminum angles, bars, channels etc onto the mounting flanges to make it fit any model in any way you want.
- Use 1/16″ thick aluminum. Just about every hardware store will have the aluminum stock you need.
Secure in place with rivets (easiest and does the job) or bolts / screws
We have a custom made hose to assist in plumbing, it is available here: Coolant Return Hose

Note: Although these rad caps with temp gauges are cool, will fit, and are cheap all over amazon and ebay, we tested them and they are inconsistent, none held up to their advertised 1.8 bar (26.1PSI) and most opened at 15-20 PSI. Stay away from these caps:

Filling and bleeding the system

On some models the heat exchanger will sit in a position that the back is slightly higher than the hose connection points, trapping air. If possible, raise the bikes front end to assist air pockets to move from the heat exchanger up towards the bottle.

Prefill the system by inserting a funnel into the hose end that is connected to the hot thermobob output. Have the coolant bottle cap open and as you add coolant it will fill the heat exchanger – flow up to the pump and through the engine – and eventually through the bypass into the coolant bottle (if your funnel is at a high enough point).
- Tip- pinch the hose closed with a plastic jaw clamp while reconnecting to thermobob.
Fill the coolant bottle to the max. Start the engine and continue adding coolant as bubbles come up and coolant level drops. Continue until you reach full operating temp then shut down and allow it to cool.
After its cooled, top off the bottle and cap it. Start up engine and as its warming up lean the bike side to side to assist in getting the bubbles out and simultaneously blip the throttle. Continue up to operating temp, then allow it to cool. This is also a good time to check for any leaks paying attention to all your hose connections.
On the first ride: bouncing on the trail will remove any remaining trapped bubbles. After the first 10 minutes stop and cool down, top off bottle and the system is fully bled ready to ride!

Worry less. Ride more. Have more fun.

NOTE: same as it is on a snowmobile- if the trail is frozen and your track is not throwing snow on the heat exchanger, your engine will begin to overheat and you will also be damaging your track and hyfax as its not getting lubricated. You must be either hitting the ditch/ banks with soft powder or have an ice scratcher to provide lubrication for your track and cooling the engine.

Tip: install ice scratchers on both sides, but use only one at a time and it provides enough snow onto the track for cooling. Riders forget to put up the ice scratchers when off the trail, and they break, but at least that way you will have a spare on the other side.

Heat Exchanger Customer setups and cooling results

Post your comments below!