I never liked the prominant radiator

[Nessism]

Water cooling assures NO overheating. The cylinders stay round which allows a tight fitting piston and promotes long ring life. Keeping the oil cool assures it doesn't break down prematurely which can cause wear on high pressure contact surfaces like cams, gears, and the like. Basically, water cooling is GOOD for durability. Oil coolers became pretty much standard equipment on air cooled motorcycle engines produced in the mid/early 1980's and onward for a good reason. It can't match water cooling though.

 

[rphillips]

Yes, I guess that sounds good, but it seems if my air cooled "83" GS1100E & my water cooled 2000 Kawasaki ZRX 1100 started on a continuous trip till one overheated, I'd think there would be problems with the ZRX far before the GS1100E, a radiator leak, hose leak, thermostat, fan or fan switch problem or water pump leak or failure. These are normal problems with all water cooled engines. The air cooled bikes have none of these parts to fail & I assume they don't overheat, as nobody has mentioned anything about seeing one overheated. That's why I brought it up, to see if anyone had had heat problems on an old air cooled bike. Assurance of NO overheating, on something that never overheats, seems kind'f useless. I don't keep up with the new stuff much any more, but are there any air cooled regular bikes anymore, not talking H-D, Guzzi, Aprilla, Piaggio, I mean Honda, Suzuki, Kawa., Yamma.

 

[Steve]

I guess when you really come down to it, ... how do you know whether it's "overheating"? :-k

Very few air-cooled bikes have temperature gauges. And the ones that do, don't really give you any guidelines on what constitutes "overheating".

You mention that you have had no problems with any of your air-cooled bikes overheating. Quite possibly true. You mentioned having problems with your KZ1300 overheating. Mine did not do that, unless I was overworking it. (2-up, towing a trailer, summertime in the western desert) Even then, as long as I was moving, the needle stayed reasonably far away from the red zone.

There is also a fundamental difference in the design and construction of air- and fluid-cooled bikes. One reason that air-cooled bikes don't seem to overheat is because they are built to a lesser state of tune. Sure, we eek as much as we can out of them, but there are limits. Using fluids (oil, water) to cool the engine allows building to tighter tolerances and higher standards, relying on the better cooling properties of the fluids. Having the engine operate within a tighter window of temperatures allows much more predictability in how to tune the engine, which ultimately results in more power.

Let's take your air-cooled arguement to a different venue. How many air-cooled cars are out there? OK, keep your search to more-modern cars, but feel free to go back 20 years. Even though air-cooled engines are plenty good, there don't seem to be very many in cars. Rather clear that liquid coolingn is better. It's just that it adds weight and complexity to a bike, which many feel is unnecessary.

.

 

[rphillips]

Didn't mean to say my KZ1300 had a problem, it never caused a "problem", in town, with a lot of stopping & going, the temp gauge would relative quickly go into the red the fan would kick on & the gauge would quickly go back down, may have had a different cooling problem that I never found, but with the new upgraded "82" model switch, the fan came on while there was comfortable space before the needle got to the red. But never ever a problem. You're correct on knowing if my air cooled bikes overheat. My idea was I've never seen any signs of anything to indicate overheating. My present CB1100F has over 50K & starts & runs as if it were new. My old "80" GS1100E, that was abused from the day it was bought new till I got rid of it at right at 60K showed no signs of anything, It may have, I don't know for sure, lost a couple lbs. of compression, but nothing I could tell. That being said, if they were overheating, but nobody could find any indication of overheating, I guess it wasn't getting too hot. Just for discussion, "not argument", Volkswagen used their air cooled opposed 4 cyl. in cars, trucks, airplanes & industrial for nearly 70 yrs. I think I remember the U.S. emission standards had something to with the demise of that little eng. And yes, you can build a hotter more powerful eng. if liquid cooled. Look at the new water cooled Kawasaki z900rs =(948cc) makes appx. 110HP vs an old air cooled GS1100E =(1074cc) @ 107 HP, but with no water system to look at nor maintain. The liquid cooled is an advantage, but depending on your application, possibly may not be an advantage in every application. And not to say liquid cooled systems are always giving problems, I know they last a very long time, but never as long as the air cooled, with no components.

 

[GregT]

There are thermodynamic limits to what you can do with an air cooled engine. Yes, a lot of those don't apply to the same extent with a water cooled one.

One of the drivers toward water cooling on bikes which hasn't been mentioned afaik is noise. Fins "ring" and can amplify engine noise. Water jackets will damp down apparent noise which makes legislators happy.

How do you tell if your air-cooled is overheating ? In my own experience, I had an iron 500 BSA racebike running on avgas at 10.5 : 1 compression start pushing it's oil out on a hot day. Pulling it down revealed a melt down one side of the piston - trapping the rings. 9 : 1 proved to be the safe thermodynamic limit for that engine. My father coined the expression that day "lubricated by external splash" quite accurate too, lol.

 

[TxGSrider]

I think the move to water cooled engines has as much to do with emissions as anything. The tolerances can be run allot closer and the temps can be held within a specific range.
When performance bikes were developing, it became an issue of them losing power as they got too hot, and so Suzuki went with Oil/Air cooling as a solution, and then later just water cooling.

I could be wrong... and may be... but my GS gives the temps of the engine based on the oil temp and may not reflect the temps of the cylinders as much as a water cooled engine where the water jackets surround the cylinders.

 

[salty_monk]

When the GS engine gets too hot the idle goes up... I had it once when stuck in traffic in downtown LA on the 1000G. Tight enough that I couldn’t lane split. Once I could get some airflow it soon disappeared.

 

[TxGSrider]

When the GS engine gets too hot the idle goes up... I had it once when stuck in traffic in downtown LA on the 1000G. Tight enough that I couldn?t lane split. Once I could get some airflow it soon disappeared.

Being a little lean at idle COULD cause that.

 

[Guest]

The Japnese over engineered their aircooled engines to run safe and proper in the hottest environments unlike Harleys and Brit bikes of the era. Once the bikes were liquid cooled the power potential was at a level just not possible with aircooling. I remember in High school the Kawasaki Tecate 250 3 wheeler went liquid cooled in 1984 and the Honda stayed aircooled for 1984. The Kaw had a big power advantage. Honda went liquid cooled for 1985.

 

[dorkburger]

I had an 85 250r back in the 90s. Quite possibly one of the funnest machines I have ever ridden. I rode it weekend after weekend with the intensity of the single, non mortgaged, still bounced instead of breaking when hitting the ground young man I was at the time. Truly a great machine.

 

[Rob S.]

I thought the main thing that enables water cooled bikes to be so much more powerful was that water cooling enables higher compression ratios.

I'll never own a bike with a radiator (a small oil cooler is cool). And I must be able to see the beautiful headers, and the engine, which must have large, functional cooling fins.

You always want what you wanted, and was cool, when you were 15-20 years old.

 

[Spyder]

I have ridden My old GS in all ranges of temperature. From 30's to well over 100. On the ridiculously hot days she would smoke like a train, and the power was noticeably down. That was the motivation for going Water cooled on my next bike. The next bike now, will be water cooled, AND fuel injected.

 

[Grimly]

I never remember seeing a modern air cooled bike overheat, or if it did we never knew it. Surely they did, but has anyone ever seen it?

Certainly did.
After a stinking hot day stuck in London traffic, the next morning the bike wouldn't start. No compression worth speaking of in any cylinder - all the rings had overheated and lost their temper.
That was the factory engine in the '79 GS850 - by that time it had done 140K and needed an overhaul. Not because of the cylinders *until then* but because it was leaking from the usual places and the PO's legacy of clutchless changing had left it with a wrecked 2nd gear dog that needed attention, so at some point it was coming out for attention.
Until that day it had started willingly enough, totally belieing its age / mileage.
When I stripped it, the cylinders and pistons were perfect.