While the debate between liquid cooled or air cooled motorcycles has been settled, for the most part, you may be wondering which is the best. While there really isn’t a better or worse category here, it really depends on the style of riding, and design of the bike.
High-performance bikes and sport motorcycles typically have liquid cooled engines. Cruising bikes and motorcycles that aren’t meant for extreme speed often have air cooled engines. Both types of engines have pros and cons, but it usually comes down to the rider’s mechanical ability and the overall style one is looking for.
Are you looking to purchase a motorcycle and don’t know which style you want? Do you simply want to know the pros and cons of each? Whatever the reason, keep reading because we will go over everything you wanted to know about air cooled and liquid cooled motorcycles.
What is Air Cooling?
A motorcycle that relies on air cooling, is just that. The engine exchanges heat with the air around it to help cool it off. There are no extra parts needed for an air-cooled engine compared to a liquid-cooled motorcycle.
Instead, the motorcycle’s engine has metal (usually aluminum) fins that draw the heat out and release it. While the motorcycle is traveling down the road, the wind dissipates excessive heat.
Benefits to this style of cooling include fewer parts that can break or require maintenance. You don’t have to add coolant, and these motorcycles are usually less expensive.
For riders that want a grittier looking motorcycle often opt for an air cooled bike. So, if style is your main concern when looking for a bike, you may want to look at air cooled engines.
What is Liquid cooling?
Liquid cooled motorcycles use the same parts as cars and trucks. If you’ve ever opened the hood of your car or truck, you’ve probably seen the radiator and the fan. You might have also seen the large radiator hoses that cycle the coolant throughout the engine.
Liquid cooled motorcycles use the same parts. You’ll have a radiator that cycles the hot coolant through it, hoses to send the liquid to and from the engine, and you’ll have to add coolant/antifreeze, and/or water.
The benefits of liquid cooling include more power, they are quieter and get better fuel economy. An engine that is liquid cooled can run harder without overheating which generates power and speed.
The trade-off is more parts that will need to be taken care of, and for some people, they don’t like the look of all those extra parts. Speaking of extra parts, what kind of maintenance do both air and liquid cooled engines require?
Maintenance of Liquid Cooling vs Air Cooling
Some owners will say that a coolant engine requires much more maintenance because of all the extra parts. Even the coolant needs to be flushed and replaced periodically. But air cooled engines require maintenance as well, and this maintenance could be more expensive because it needs to happen more frequently.
Liquid Cooled Engine Maintenance
The coolant should be checked regularly and topped off anytime you see it getting low. Besides that, it should be changed out at least every two years or around every 20,000 to 25,000 miles.
The hoses need to be replaced occasionally as well. The rubber will become hard, can crack, and lead to coolant leaks, so it’s advised that these get replaced occasionally as well. This cost is relatively negligible compared to some major repairs, but it is another expense you’ll have to think about.
You also have to get repairs made if the radiator gets damaged or springs a leak. Water pumps will fail over time and will need to be replaced. It’s these problems that air cooled motorcycle owners like to point out.
On motorcycles, the valves need to be inspected and adjusted regularly. This isn’t something that anyone can do, and typically requires a trip to the mechanic. Fortunately, for liquid cooled engines, this task only needs to be taken on every 12,000 to 20,000 miles or more.
To be sure when your bike needs this, check the owner’s manual as the exact mileage depends on the specific make and model.
Air Cooled Engine Maintenance
Here there’s not much that needs to be taken care of because there are no extra parts that can break. You’ll never have to replace a radiator that gets punctured with road debris or fix a broken water pump.
The problem comes with the valve inspection and adjustment. On air cooled motorcycle engines (like the Ducati Scrambler), the valves get hotter and have to be adjusted much more often. Depending on the make and model, you may have to get your valves adjusted every 6,000 to 12,000 miles.
On average this “simple” maintenance cost will run you around $300. Depending on how much you drive your bike, you may have to shell out that money twice or even three times a year.
Okay, so air cooled engines may cost a little more overall to operate, but what about other pros and cons such as power, noise, and style?
Which Has Better Power Generation
Because liquid cooled engines are able to run at lower temperatures, they are able to produce more torque, more peak horsepower, and faster speeds than air cooled engines. Liquid cooled engines have a higher heat tolerance and the parts don’t expand as much as a result of excessive heat.
The sport bikes—sometimes called “crotch rockets”—have liquid cooled engines so they can produce more speed and power. Also, most motorcycles that displace a liter or more (1,000 cc engines) typically have liquid cooled engines.
Air cooled engines just can’t dissipate heat quickly enough to make them extremely powerful. There’s certainly nothing wrong with them as these motorcycles will still see triple-digit speeds, but how often are you really able to get to the race track to fully open up the throttle?
How About the Noise?
Here the advantage goes again to liquid cooled engines. The coolant in these motors acts as a sound insulator and helps to reduce the noise of the motorcycle.
Of course, if you’re partial to Harley Davidson motorcycles and that rumbling, chest throbbing, ear-splitting “blap-blap-blap” sound, then, by all means, find yourself an air cooled beast.
Sometimes that rumbling sound is what you need to let other drivers know you’re nearby. All too often cars and trucks don’t see motorcycles and can cause accidents when they suddenly shift lanes. But if your chopper is rattling their windshield when you get close, they will know you’re there.
Which Type Carries the Best Style?
As always, style is subjective and it depends on the individual. I personally prefer the look of a cruiser or a custom chopper compared to the sport or supersport bikes. That’s just one opinion out of millions.
For those of you who like the look of a sleek, aerodynamic bike that is enclosed with sharp, air-cutting designs, you’ll prefer a bike that’s liquid cooled. These speed machines need the coolant to maintain the higher revving, more powerful engine.
Maybe you like the big, chunky beasts that look like they’ve been hitting the gym and downing every steroid it could get its spokes on. These too usually have a liquid cooled engine to keep the massive motor cooled off properly.
Air cooled motorcycles are bikes that represent simplicity and fewer high-tech components. Some of these bikes are more gritty looking. They may appear stripped down and laid bare instead of encased and enclosed in other parts and aerodynamic pieces.
Most times single-cylinder motorcycles or parallel twin engines are air cooled. So if these engine styles are what you’re looking for, then you’ll end up leaning more toward air cooled motorcycles.
There’s no right or wrong when it comes to style, it all depends on what you as the individual are looking for.
Now, let’s touch on the ever-popular V-twin engines.
What is the Best for V-Twins?
The iconic V-twin motor can be either an air cooled, or liquid cooled engine. Many Harley Davidson bikes are known for being air cooled V-twin bikes. It’s a classic design that was first invented in 1902, way before there was a radiator and liquid cooling.
The problem with air cooled V-twin engines is all the air hits the front cylinder first, while less air is able to get to the back of the second cylinder. Because of this uneven cooling, air cooled V-twin engines aren’t able to be pushed as hard as liquid cooled versions.
Liquid cooled V-twin motors are able to pump out higher compression, faster speeds, and more power. So here we have the liquid cooled engine that comes out a little bit ahead of the air cooled counterpart.
An exception to this rule (as there usually is) is the Moto Guzzi motorcycle. The model motorcycle has a transverse mounted V-twin, air cooled motor. Because it’s turned 90 degrees, both cylinders benefit from the same amount of air.
Surely the air cooled engine weighs less, and such should have the advantage in that category.
How About Weight?
Yes indeed, an air cooled motorcycle is lighter than its liquid cooled counterpart. Air cooled motors don’t have a radiator, water pump, hoses, quarts, or even up to a full gallon of coolant, and more parts. All of these added components tack on extra weight.
But let’s look at how air cooled engines actually dissipate all that heat. On the outside of the engine, cylinders are layers of metal fins that aren’t on liquid cooled engines. This adds extra weight to air cooled engines.
Some motors have an extra inch of metal on them to act as a heat sink. Heat is the number one enemy of engines and they have to be able to get rid of it quickly or it can cause several major problems.
While the liquid cooled engine has more parts overall than air cooled engines, they aren’t that much heavier, so the full-weight advantage is negligible. Air cooled engines are slightly lighter, but you’re not likely to notice the minimal difference.
How to Protect Your Bike Over the Long Term
If you’re worried about an air cooled motor overheating, keep in mind that these types of motors have been in use since the 1800s. Motorcycle companies have only recently really started adding liquid cooling options. Also, many air cooled engines have safety features that prevent the engine from overheating.
With that said, there are some things you can do to help prevent an air cooled engine from overheating and lasting longer. The most important thing you can do is stay on top of oil changes. The oil not only lubricates the engine but in air cooled motors, it actually helps to cool it off.
Keep your oil fresh, and change it regularly. Especially after use in extreme conditions. Are you stuck in traffic often, do you have a lot of stop signs and traffic lights that keep you idling longer than you want to be? Change your oil more often, or switch to synthetic oil.
You can even install an aftermarket oil cooler. It’s a radiator for your oil and helps to cool off your air cooled engine better and faster.
Be sure your idle is set lower, and if you are in a traffic jam for a long time, go ahead and shut it off until you start moving again.
For liquid cooled engines, be sure to keep the coolant topped off and at the proper mixture. Many coolants need to be mixed with water to reach their full cooling potential. Check the instructions on the bottle to see how to mix it, or purchase pre-mixed coolant.
Also, be sure to flush the coolant system when the manufacturer recommends it. These steps will help to keep your engine running cooler for longer.
Like any two comparisons, there are pros and cons to each. Air cooled motorcycles don’t have as many parts and weigh slightly less than liquid cooled bikes. On the other hand, liquid cooled engines are able to produce more power and speed.
Both types have different styling, and this depends on what the rider is looking for in their bike. Are they looking for a “rocket ship” or a cruiser that looks like a vintage motorcycle?
It really comes down to your riding style. Do you want a bike for cruising, and leisurely rides, or commuting back and forth to work on sunny days? If so, an air cooled engine might be right for you.
Are you looking for power, speed, and slick styling? If so, you may prefer a liquid cooled engine. Either way, there is no real right or wrong, only what feels best for you.
I’m William Guzenski, ASE certified master automobile technician & automotive expert. I love to attend race events and car shows throughout the country. I also loves to travel 40-foot motorhome, exploring abandoned mines and ghost towns. I’m currently building another car for Bonneville Salt Flats and will be campaigning a drag car at several events.