Running Hot (Part 1)

This is the first article in a series entitled ,”Running Hot” by Chad Hensiak

In this article I would like to address an issue that a lot of my fellow Harley riders are faced with.  Running too hot!!  We all know our engines feel hot to us but how hot are they actually running?  It is not uncommon for a TC88 (twin cam 88 cubic inch) motor to reach temps of 230 – 260 degrees during periods of idle.  I know that the TC96 engines of late can run even hotter!  This can put an extreme strain on the oil and all the little metal bits that make up an engine.  The optimal running temperature for your engine is around 195 – 210 degrees.

Most of us will never know how hot we run because there are almost no Harleys that come stock from the factory with an oil temperature gauge, however Harley did fit our FLH and FLT models with an almost useless outside air temp gauge?  You can purchase a kit from Harley that will allow you to take out that useless outside air temp gauge and put in a useful oil temp gauge, the downside to this is it is around 300 bucks depending on where you purchase it, and it is beyond the realm of most shade tree mechanics to install at home.  So you will most likely end up forking out some more cash to pay your dealer to do it.  And after all that you would only see that you are running too hot and still have to spend more money to correct the problem.

There is a slightly less expensive temp gauge option out there, you may purchase an oil dipstick with a digital read out that tells you your oil temp.  The downfall to that is, you will have to look down and try to read it from the seated position, or get off the bike to read it.  I don’t see that as a good situation to be in while trying to ride through stop and go traffic.

Now we need to understand the basics of an oil / air-cooled engine.  Without getting too far into greasy details of an internal combustion engine that is not liquid cooled (that is without a radiator and coolant) we need to understand that the Harley V-twin engine depends on two main things to keep it cool.

First: Moving air.  I say moving air because as we all have found out when we are stuck standing still for only a few seconds the temp of our engine seems to soar.  This is partly because heat rises so we feel it more as we sit above the engine at a stand still, but mostly because as the engine sits and runs at idle the air that was rushing thru the cooling fins on the outside of the motor’s cylinders, or “jugs” as they are called, has stopped moving and is no longer carrying away the heat that the engine creates, allowing the engine temp to soar.

Second: Oil is your engine’s lifeblood!  I cannot say enough about the importance of keeping your oil clean and cool.  The single most important thing you can do to save your engine from heat and prolong its life as a home mechanic is to change your oil often (at least as often as your owners manual tells you to.)  Use high quality full synthetic oil (like Amsoil) in engine, primary and transmission.  No, you may not go down to your local farm and barn and just run whatever is on sale!  Auto grade oils do not perform the same in modern hot running Harley V-twin engines as the recommended motorcycle oil, if there is no bike oil available, car oil is better than running your bike low or empty, but I still recommend getting to a bike shop ASAP to get the required motorcycle oil.  Every bike has its own oil needs so check your owner’s manual or ask a dealer what weight you should use.

An oil change is useless without an oil filter change!  With the invention of high quality full synthetic oils lasting twice as long as conventional oils some people do not change the filter until they change the longer lasting oil thus making the filter work twice as long as it was designed to. Example: if your Synthetic oil lasts 6,000 miles without needing a change, I would recommend changing the filter at 3,000 miles. The filter cleans the oil by confining the contaminants the oil carries in it’s filtering media, when the filter is full of contaminants oil no longer gets filtered properly allowing dirt to circulate through the engine and slowing the vital flow of oil through the engine.  In short, your oil can’t cool or lubricate what it can’t get to.  It’s kind of like the arteries in your body, too many good old American cheeseburgers and deep fried goodies, and you have a clog in your body’s filter, you can get all the blood transfusions (oil changes) you want but it won’t stop a heart attack from killing you.  Trust me your heart and your bike will thank you for that bit of info.  I will go into more on how to cool off your oil in the next installment of this series.

Another factor that contributes to a hotter running engine is the bike engine’s A.F.R. (air to fuel ratio.)  This is simply the amount of fuel your bike’s fuel delivery system be it a carburetor or an E.F.I. (electronic fuel injection) will send to your firing chamber during the intake stroke.  Harley has to set its A.F.R. ratio on the lean side of things to meet emissions standards and to ensure the best mix of miles per gallon while still producing the most horsepower a stock bike can produce.  People often add aftermarket mufflers, high flow air filters thinking that they are adding performance and horsepower.   When in reality adding these things without getting you A.F.R. corrected to compensate for the added items makes the engine run even leaner and hotter than the already lean factory settings.  A factory engine needs more fuel even without adding a high flow air filter or high flow mufflers.

In the next month’s edition of this series we will get more into oils and what they can do to cool off our engines.

As always ride smart my friends  -Biker Chad