Accident Scene Management / Road Guardians

Running Hot Part III

Motorcyclist riding

Running Hot Part III
Written by: Biker Chad

In the last part of this series, we discussed the benefits of using good quality synthetic oil.  Now that you know that synthetic oil will definitely keep your engine, primary, and transmission cooler, while helping them last longer.  We can move on to discuss some other things to help cool off the Harley V-twin engine.

Even when running great synthetic oil like Amsoil in your engine’s crankcase you can still go one step further to help your engine stay cool.  I always run, and recommend to every Harley owner that you run, an oil cooler.  There are a lot of companies that offer oil coolers, so how do you pick one?  To help answer that question I wrote you this article.

First, the more surface area you have on the oil cooler the more effective it will be at cooling the oil.  Six-row oil coolers help a lot, I recommend an eight-row cooler, ten-row oil coolers can be better still.  Keep in mind however, too many rows can drop oil pressure, this is why I recommend an eight-row cooler.  On built up engines with a high volume oil pump pressure drop from larger oil coolers should not be a factor.

Second, good oil coolers need to mix the oil to keep it at a uniform temperature, and evenly disperse the oil in the cooler.  This is achieved by use of a “turbolator” in the oil cooler.  Make sure any oil cooler you get has a “turbolator” feature.

Third, an oil cooler needs a thermostat.  It is possible to over-cool your oil.  Over-cooling can be as bad as being too hot, or worse.  An oil cooler thermostat works by only letting the oil flow into the cooler when it needs to be cooled, thus keeping the oil from over-cooling in colder weather.  So make sure you get a thermostat with any oil cooler you buy.

There are several manufacturers out there that make oil coolers for Harley engines.  Jagg and Harley-Davidson are the two I like most.  Both are close in price, design and function.  I seem to install Harley’s oil cooler more often only because it comes with a thermostat in the kit.  With a Jagg cooler you need to purchase a thermostat separately, I have used both and recommend either manufacturer.

Oil coolers do work best when you are moving as it relies on moving air to cool it, just like your engine.  However when you are not moving, the added surface area of the cooler will still help to keep the oil temps down better than no cooler at all.  A smart guy would figure out how to incorporate a fan to blow air thru the oil cooler, much like a car’s radiator fan.  Maybe we just found a good use for the parade fan Harley sells, ha ha!  Either way, oil cooler technology has come a long way since the days when we used to take the transmission oil coolers from junked cars and mount them on bikes for home made coolers.

Oil coolers are relatively easy to install for the at home mechanic.  Although some special tools may be required, I do believe it is a job you can do yourself to save some money.

Once your oil cooler is installed you should check the oil level after you fill and run the bike till it reaches normal operating temperature.  This will ensure you have not under filled the crankcase due the cooler being filled with oil.

-Biker Chad


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