No ... as an air cooled engine gets hotter, it will transfer more heat to the surrounding air, as the temperature differential will be greater. The hotter the engine gets, the greater the temperature differential with the stationary air next to it ... and the greater that differential, the more energy in the form of heat will be transferred to that air. Eventually (as the engine gets hotter) the amount of heat being transferred to the air will be equal to the amount of heat being generated by the engine i.e. there will be an equilibrium temperature that if you left the bike idling, it would eventually reach. If the outside air was cold, i.e. it was sitting outside a starbucks in Tromso Norway, in the middle of winter, the equilibrium temp the bike would reach would be lower than if you left it idling in the Sahara in the middle of summer. Thats because the temperature differential between the idling engine and the air is greater at -30 C than at +50 C.

I disagree ... efficiency of an engine impacts on how much fuel to have to carry. That means less range, and more weight. So the efficiency of the engine is a major consideration point for me. An old air cooled, carbed bike which may be more than 30% less efficient than a modern water cooled fuel injected bike will have to carry 6-7 kgs more fuel for the same range.

The water in a cooling system will weigh about 1.5 kgs. As opposed to the 6-7 kgs in extra fuel you carry on an aircooled bike of the same power. Sure the radiator has small amount of weight, but so do the metal cooling fins on an air cooled engine.

Realistically, compare the weight, power and efficiency of the BMW Rotax 800cc engine vs a BMW air cooled 1000 cc boxer engine (the last properly air cooled engines they made) ... its slightly lighter, 40% more powerful, and probably at least 40% more efficient too. The range on a 16 litre F800 would be about the same or more than 24 litres on a airhead boxer. Particularly in challenging conditions when range is critical.

I dont have a fancy radiator guard on my X-challenge yet dont consider it a fragile part of my bike ... Come to think of it, I have not had a radiator or water cooling related problem in nearly 20 years of adventure motorcycling. The air cooled engine thing is a red herring. Its one of the great adventure motorcycling "wives tales" that is just not borne out by reality. I dont recall reading about anyone on the HUBB who needed help because his radiator got holed. Even if there was the odd rare case, fixing a holed radiator is something that you could get done is pretty much any 3rd world village anyway.

If you happen to love old air cooled engines, then by all means use them. I know plenty of boxer enthusiasts whose preference is not to ride anything different because they love the character. Choosing them for character is one thing, or to choose a bike that you like that happens to be air cooled ... great , by all means take an air cooled engine. Nothing wrong with it.

But its ludditeism and just closing eyes to the reality to suggest that old air cooled engines are better than water cooled, fuel injected engines for adventure bike travel.

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