To all you Air-cooled riders out thier....How would you know if your engine is "over-heating"??? Trust me , while your buddy;s radiator fan is going ON and OFF keeping his engine coolant the right tempature, your engine is just as hot! and just because your motor doesnt SeiZe UP or your head doesnt glow red, doesnt mean your motor isnt "over heating". I can garrentee you unless you have a 100% stock ATV, you have overheated your air-cooled engine many times and you never knew it.

Water cooled engines can run higher compression ratio's, and higher RPM's because of thier better cooling systems. This is why we have the 450R(honda) and a YFZ450 today, because water cooling made it possible. Other wise we would all be riding 350 Warriors[img]i/expressions/face-icon-small-wink.gif[/img]



Technology is a wonderful thing!! embrace it...


biggerisbetter.[img]i/expressions/face-icon-small-smile.gif[/img]

 

good topic

 

biggerisbetter is very, very right. It is very difficult on most quads to know if it is overheating.
After plowing snow with a Bayou 300 for four years, and having it overheat many times to the point
of charring the oil and requiring as many as 3 oil changes a month, I will never again own a air cooled
quad that doesn't have an oil temp sensor and light or audible alarm. The only way I knew it was overheating was the oil color and the smell of fried oil- black as coal, and sometimes only a week old.

 

Many interesting points here. At least a couple people have made the comment that liquid cooled engines run tighter tolerances. I have not always found this to be true. I have a lot of experience measuring and fitting various engines. Air cooled engines are often fit VERY tight, for example, the standard piston to cylinder clearance on an 86 trx350 (air cooled) is as little as .0006 inches (that's little more than half of one thousandth for you math challenged debaters). I don't know of ANY Honda engines liquid or air that run tighter specs than that. And in general, you find the specs not so different from air to liquid. This is probably in part because the liquid cooled cylinders are slower to heat up and expand, making them more prone to cold siezure. You really start to see this in liquid cooled snowmobile cylinders, particularily the nikasil ones (sheds heat fast, so is slow to heat up). The mfg. has to match the piston expansion via content of different alloys to the cylinder. Lets take another spec like valve clearance, the same 86 trx350 runs .003 inch valve lash, while a newer Rincon (liquid) the lash is set to (I think) .006 and .009. It isn't the liquid cooling that gives the machine bigger boom, but because it is more efficient at getting rid of the inevitable extra heat, it allows the mfg. to get more radical with a given cc, keep in mind that a small amount of this extra hp is absorbed by having to run a water pump!! Anyway, I really prefer liquid cooled, for consistent running, and longevity, but I can see the downside too (leaks, plugged rads, water pump seals, weight, complexity, etc.)

 

My Foreman has a good sized fan on the oil cooler. It seems to move a lot of air over the cylinder and head when operating. I assume this helps to cool the engine at slow speeds?