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Air Cooled vs Liquid Cooled Motorcycles

Air Cooled vs. Liquid Cooled Motorcycle Engines

One of the considerations to make when buying a motorcycle is the difference between air cooled and liquid cooled motorcycles. Depending on where and how you plan on riding, a motorcycle’s cooling may play a large part in your decision to buy, and how much you’ll appreciate your machine.

  • Air cooled motorcycles run noisier.
  • You’ll tend to see air cooled more on cruisers, as most cruisers typically run at lower RPMs then sportbikes.
  • Sportbikes tend to be liquid cooled.
  • Air cooled engines provide more simplicity, representing one less component which could break, need to be replaced, or need servicing
  • Liquid cooling rads are sometimes fragile, and external or aftermarket oil-coolers can also be expensive and could break in an accident.
  • Air cooled bikes may be cheaper.
  • Air cooled motorcycles are likely more feasible for single cylinders (big thumpers), or parallel twin engines.
  • In V-Twins, the back cylinder could remain hotter than it otherwise would.
  • In liquid cooled engines, the circulating liquid evens-out hot spots in the cylinder head. This is better for detonation control and for emissions. The combustion chamber surfaces can be kept hot enough to encourage more complete combustion, but not so hot so as to promote detonation or high NOx emissions.
  • Liquid cooling is better for long-term durability since it allows tighter build tolerances.
  • Liquid cooled engines transfer the heat to the rad at the front of the bike, making a long ride or a traffic grid lock more tolerable for the rider.

Air Cooled Motorcycle Engine

Some additional notes, from the comments section:

  • Air cooled engines run richer, making them less efficient and more polluting.
  • Water jackets in an engine act as sound insulators therefore liquid cooled engines are quieter than air cooled engines.
  • Liquid cooled bikes can rev higher because they have higher tolerances due to their ability to self-cool.
  • Air cooled require less maintenance (liquid coolant requires coolant change every 10,000 km).

What you’ll want depends entirely on your ride. Sportbike or other high-revving engine, you may want to make sure you’re getting something with liquid cooling. Scooter or cruiser can probably get away with air-cooling. Many people say Harley-Davidson Sportsters never overheat, but if they do get hot, there are always things you can do, such as switching to a full synthetic motorcycle oil, or adding an OEM or aftermarket oil cooler.

Personally, I switched from a japanese, liquid cooled motorcycle, to an air cooled Harley-Davidson. I was a student riding to downtown Toronto, and the bike just got far too hot for me. I switched back to liquid cooling. Of course, I live in the most densely populated city in the country, so your experience on an air cooled motorcycle may be far different from mine. In fact, Harley-Davidson has the largest share of motorcycles over 750cc on the market, and the vast majority of their line up is bikes powered by air cooled motorcycle engines.

It’s not about right or wrong, or good or bad, it’s about letting you know what the differences are.

Have other questions?

You might also be interested in articles such as Disk Brakes vs. Drum Brakes, or Shaft Drive vs. Belt Drive vs. Chain Drive. Tap into our library of motorcycle knowledge here, or ask a question in the comments area below!

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14 comments

  1. water cooling on a bike is nonsense. Aircooled bikes don’t overheat

    • I was sitting in traffic at Myrtle Beach. Couldn’t move. I had to pull over and turn off the bike to cool (in 100 degrees no less). It was WAY over-revving. Then, I’d move a little, turn it off, move a little, turn it off.

  2. Hello,

    Air cooled engines need much richer carburetion to cool them this means they pollute much more than liquid cooled engines. Liquid cooled engines can operate with carburetion set to burn all the fuel in the mixture. This chemical balance is called stoichiometric combustion where all the fuel is burned. Air cooled engines will never run with stoichiometric combustion because they would quickly overheat.

    Water jackets in an engine act as sound insulators therefore liquid cooled engines are quieter than air cooled engines.

    Its inevitable that governments will regulate motorcycle tailpipe emissions which will be the end of air cooled motorcycles.

    Rgds
    Eric

    • I am with Eric on this. Harley and those who have followed its lead have perfected the air cooled V-twin engine to the extent it can be. They are relatively clean and powerful, but a water cooled bike which allows tighter tolerances will pollute less and rev higher, producing more horsepower. The proof is riding on the road now. Look at the amazing power difference between Harley’s lower displacement, water cooled V-Rod and their larger displacement cruisers.

      I am riding my second Harley touring model and I love it, but I think by the time I get around to getting my next one it will be water cooled and it likely won’t have push rods.

      Jefe Smith

  3. musictoone@yahoo.com

    I can’t go back to air cooled. loved my yamahas but liquid cooling has been awesome in the las vegas desert. my vtx has a fan that comes on just like a car to keep cooling even if at a stop light. a few more parts? yes, but way worth it. if I didn’t live in the desert? then air would be fine I think.

  4. Currently own Harley Road King(103) and it gets oppressively hot. I’ve had liquid cooled bikes and never had a problem with heat or cooling parts failure. I’ve got a friend with a 2014 Tri Glide(cooled heads) and they say it still gets very hot. Liquid cooled victory touring bike here I come!

  5. Interesting discussion. Although I have had two air cooled bikes in the past, I had not really thought about the relative advantages and disadvantages in relation to water cooled engines before.

  6. tnx everyone, pls i am new in bike world and i want to get one for myself, please advice me on which to buy, air coolant or water coolant?

  7. One advantage air cooled motors have is easier maintenance, Another advantage the air heads have is looks. I find a nice set of jugs sticking out into the air a thing of beauty! Look at the Moto Guzzi, the older air head BMW’s, Triumph, Norton’s Harleys ect. However if you want to make a lot of power and do it reliably liquid cooled is the answer.

What do you think?

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