Besides the look factor of a radiator (which is a large consideration), it's adding another system to the bike that needs maintenance and/or could fail - catastrophic failure is a possibility.
Keep the bike simple and easy to work on.

 

Thanks for the help guys!!!

 

Much in life is either a trade or a compromise.

Air (and oil) cooled motors are typically lighter and less complicated, lacking radiators and thermostats, water pumps and water. Therefore less maintainance, less to fail. But they suffer from hot spots. Areas that don't have cooling fins and less exposure to moving air when going slow. They can get very hot and lose HP as a result and suffer excess wear in the hot spots. Air cooleds also warm-up slower on cold days and while cold is when a motor suffers the most wear and generally (although many will argue) are not expected to live as long as a result. It is also difficult to cool any motor at extreme speeds. Even the sport bikes with radiators need bigger radiators for racing to keep from overheating.

Compromise. If you go real fast, you had better not wear your tassles!

The best power-to-weight ratios, least moving parts etc. are found two-strokes motors. Like chainsaws... but that's another thread.

 

To add:

Water cooling also allows tighter tolerances and there for higher performance. As well as has been mentioned water cooling will always have advantages over any aircooled motor. The extra hardware needed is a small price to pay from all the benefits gained.

 

Liz, air cooled is better from the styling and simplicity standpoints. That's it.

Air-cooled engines are the essence of a Harley, some say. (When the V-Rod came out, I couldn't believe the uproar and anger over the use of liquid cooling. One old-timer I know said he would never buy another Harley because of this. So he buys a Honda VTX.)

You would lose the current style, and simplicity. (Style is subjective, though...I love the V-Rod, myself. But air-cooled bikes do have cleaner lines.)

There is much to gain with liquid cooling. Liquid-cooled engines are higher powered, quieter and their emissions can be more easily controlled, because a liquid-cooled engine is more temperature-stable and is built using tighter tolerances.

If Harley wasn't under the EPA gun, you would probably never see an air-vs-liquid debate.

 

or they might go the way of bmw, air / oil cooled, the most epa complient bike on the market.

 

My eye starts to twitch everytime I see that Harley jug of coolant at the dealer. I had to break down and but a bike with fuel injection but I will be damned if I am ever going to ever buy a water cooled Harley. Just my opinion from a stubborn middle aged fart!

 

weight and horsepower, weight: the water pump, hosing,radiator and coolant all add weight. extra weight means slower speeds.
Horsepower: it takes extra power to turn the waterpump and push that coolant through the system, that power is taken away fron the wheel.
also factor in added maintenece costs, Checkign coolant, replacing blown/swollen hoses, radiator damages *pin holes,cracks etc* as well as the possiblity of freezing the coolant in the winter, messy clean ups etc

 

Bring on the water cooled baggers. W/lowers the radiator will be pretty non de-script. The cooler running and ability to build more power, easily, is a big plus to water cooled. Have you ever heard a v-rod with engine work and a good set of dual pipes? wouldn't know it was water cooled. As far as problems with water cooled systems, the metrics don't have any more problems than air cooled. Would you rather drive a Corvair or old VW, or a Cadilac?

 

I would rather ride an air cooled Vtwin just the way I have been for all of my adult like. This radiator talk is making my eye twitch again....