Since Iíve been writing these tech-tips, Iíve found that the more opinionated I become with my point of view, the more responses I get in the mail from our loyal readers. Opinions are interesting things. Some opinions are formed by ignorance, others by experience, and some are just passed down from generation to generation with little thought to the relevance of the belief associated with their chosen point-of-view.
Well this month, Iím going way out on a limb. Iím going to use a little of my own personal commonsense and let you know how I feel about oil-coolers. Hereís the official disclaimer: this is my opinion, and not the opinion of the publisher or anyone else. You are welcome to share in my opinion, think Iím a genius, recommend me for a gold star, and feel free to shower me with praise next time you see me. At the same time, you are more than welcome to disagree with me, tell all your friends what an idiot I am, and do whatever ultimately makes sense to you. Different opinions are what make this an amazing country to live in, right?
This time of year, I see a lot of people wanting to make sure that their bike does not overheat. If you own an American bike, and itís not a V-Rod, youíve got an air-cooled motor. Most of our metric bike friends on the road, and the V-Rod, have water-cooled engines. As basic as this sounds, either water and air or oil and air must cool your bikeís engine. Why? Iíll tell ya. Because you are being propelled down the road by an internal combustion engine. Combustion (the explosion) of your fuel (gasoline) moves the pistons in your motor, which generates heat. Then on top of that, the movement in close proximity of the internal components of your motor (rods, pistons, gears and the like) creates friction, which generates more heat. If you donít control the heat associated with these mechanical functions, all this metal stuff in your motor will just melt together and youíll end up cursing on the side of the road. Not good.
If you were reading closely, the common cooling feature found in either water-cooled or air-cooled engines is AIR. Air is the common denominator that cools your motor, whether you have just oil running through it, or oil and circulating water (anti-freeze coolant) flowing though pockets inside your crankcase. The ultimate goal is to dissipate the heat generated in your motor into the atmosphere.
If youíve got a water-cooled engine, youíll be sporting a radiator somewhere on your machine. Normally itís a rather ugly, but required, piece of gear aptly named because it radiates the heat captured in the water thatís circulating through your motor. A typical radiator is composed of thin circuits of compressed tubing through which the water or "coolant" flows. Air passes by the radiator fins and the heat energy is dissipated into the atmosphere so the coolant can once again flow into the motor to cool the hot cylinders. If your vehicle is sitting still and no air is flowing through your radiator, heat will build up and youíll overheat your motor. To alleviate this condition, vehicle manufacturers place electric fans in front of your radiator to assist with the flow of air to keep the cooling process happening. Flowing air is the most important component to transfer the heat. If youíve got no airflow through your radiator, youíll overheat.
Your American V-Twin is a time-honored, incredibly good-looking design, which incorporates an air-cooled motor. Confused yet? Yes, air does cool your motor, but itís also the oil in your motor that is circulating and dissipating the heat being generated. Most V-Twins have only a 3-quart capacity of oil that circulates in and out of the motor. If youíre a quart low on oil, youíve reduced your cooling capacity by about 30%. Thatís why it is very important not to run your bike low on motor-oil; even more so when itís hot out. The oil is also flowing at a relatively low pres sure in your motor. The oil pump, depending on the oil temperature, generates only 5 to 15 pounds of oil pressure. If your oil is extremely hot, youíll lose oil pressure, which results in engine damage. Sounds like you need an oil cooler, right? Well, not so fast. Iím still trying to get to my point here, bear with me.
Air is the key to cooling your V-Twin. Thatís why your motor has large fins all around the cylinders, which add more surface area. This additional surface area that you see on your Harley-type motor works just like a radiator on the water-cooled motor. Air passes over the fins when youíre moving and that cools your engine and itís components, including the oil circulating from your oil tank into your motor. If youíve got an oil cooler, it will add an additional "radiator" type contraption to your oil circulation system to dissipate the heat stored in the oil.
As much as youíd like to run out and buy an oil-cooler, Iíd advise you to keep your wallet in your pocket. Now Iím finally getting around to my opinion regarding why I think you should skip putting an oil-cooler on your bike (see disclaimer above). An oil cooler only works if youíve got air blowing through it. When youíre moving, an air-cooled V-twin motor cools just fine because youíve got air blowing through it. The same principal applies to your accessory oil-cooler; it needs air to circulate through its radiator to cool your motor. The problem is that Iíve yet to see an oil cooler designed for a V-Twin that includes an auxiliary fan, like a wate r-cooled radiator.
About the only time your bike is going to overheat is when youíre sitting still, low on oil, and thinking about another route to take to avoid the traffic jam youíre stuck in. If youíve got an oil-cooler on your bike, sitting still with your motor running, youíll be reducing the oil pressure by forcing the oil through the cooler. The whiz-bang oil cooler wonít be cooling your oil because it has no air circulating through it, so youíre in double Ďheatí jeopardy. Plus youíve added about 4 more oil hose fitting locations creating more places for oil to leak from your bike. If youíre leaking oil, youíre loosing the cooling property and contents of your oil-bag and reducing the ability of your air-cooled motor to cool properly. Note: Harleys donít leak; they just mark their spot.
Last but not least, I can hear all of you ĎOil-Cooler Advocatesí yelling right now that itís 120 degrees out here in the desert, you need all the help you can get. Bah-humbug. Your V-Twin is well designed to run at around 215 degrees of oil temperature. If the ambient air temperature is 90 or 120, your motor really could care less as long as it has air blowing through it regardless of the air temperature. Iíd rather have more oil pressure lubricating my internal combustion engine to keep me going, than a $150 oil-leaking accessory bolted to my bike thatís not helping me cool my motor.
In summary, I think the best thing you can do here in the Desert Southwest is change your motor oil often, make sure your oil level is topped off, and avoid traffic jams. I also run 25/60-weight oil in the summer, vs. the standard 20/50-weight oil normally used in your late model bike to add an extra margin of heat protection that the higher viscosity oil will provide. I say keep your money in your pocket next time somebody tries to sell you an oil-cooler. Spend your cash on a date to have a great dinner and a movie with your friend or mate when the weather heats up. Give them a ride to the show on your bike, have a good time, the air-conditioning in the theater is amazing this time of year. Thatís way cool.
Keep the rubber side down.
- John at Steeds
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