Q&A

Is forced air cylinder head cooling better than an engine oil cooler?

It’s hard to give a definitive answer about what is better. I use both engine cooling fans and a fan assisted oil cooler on my bike.

Cooling the cylinder head attacks the source of engine heat. The cylinder head is where the combustion explosion happens, and any heat that doesn’t escape through the exhaust system has to be lost through the cooling fins around the engine or passed to the oil system. Forced air cooling helps the engine cooling fins do their job better in slow moving traffic.

Cooling fans can be fitted quickly and easily with a minimum of fuss. There is no engine modification, just a simple bolt-on. You can simply remove them in the winter if you want. An oil cooler requires more effort to fit, usually with an adapter fitted at the oil filter. It also introduces external oil lines which can potentially leak.

How are the fans mounted?

cooling fans look greatThe high strength plastic mounting plate fits on the horn mounting bracket – just a single nut to remove or fit. The complete unit weighs just 750grams.

The mounting plate has been designed to aim the airflow directly at the cylinder heads, taking advantage of the air passages around the rocker boxes. Each fan is angled at 22.5° from vertical to align with the fins on the 45° vee twin engine.

Do you provide a temperature sensor to control when the fans are on/off?

No, there is just a simple switch on the side of the mounting plate, easily reached when riding.

I think the rider is the best judge of when the fans are needed. It’s easier to keep an engine cool than to cool it once its got hot. So, if you can see you are coming up to some slow moving traffic, switch the fans on before the heads get too hot.

Could these fans cool the engine too much?

That’s very unlikely if you use them sensibly. The fans only blow ambient air. That’s the temperature range your bike is designed for.

What is the best way to use the fans?

First make sure your bike is properly tuned. An out of tune bike may run hot, and no amount of puffing and blowing will fix that.

The fans are designed for city riding. Turn them on when running in slow moving traffic, below, say, 80km/h. Turn them on before your engine becomes hot – it is easier to keep an engine cool than to cool it down after it has become hot.

How powerful are the fans?

grill showing plenty of air flowThe manufacturer claims airflow above 180cfm (cubic feet per minute) for each fan – that’s over 360cfm in total.

Rated life expectancy is over 70,000 hours. (That’s 7 million kilometres at 100km/h)

Do they work in the rain?

Yes,but you probably won’t need them when it’s raining. Water is a very effective coolant and your engine will run cooler in the rain. It’s probably unwise to deliberately spray water on a hot engine with the fans.

Are they noisy?

Yes. The fans operate at around 13,000 rpm (that’s why they pump so much air). They are rated at 74dB. You will hear them running when you are stopped at the lights but not so much when you are moving.

How are the fans powered?

fans plug directly into battery tender plugThe kit includes a connection to the pigtail lead fitted by most dealers for trickle battery chargers. (This lead can also used to power a variety of accessories, such as an air pump.) You will need to upgrade the fuse to 10 amp (included) as the fans draw 48w each.

So there is no mucking around with wiring harnesses and switches, no interference with your wiring system. Just bolt on, plug it in and go.

This is a very simple way to get power to the fans, but it means they are wired directly to the battery and not through the ignition switch. The downside is that you will flatten your battery if you leave them on when you’re not riding. Don’t do that.

fans plug into existing wiringYou can find alternative ways to provide power through the ignition circuit if you wish, perhaps through an accessory plug if your bike has one.

How do they compare with the competition?

I don’t have samples of competitors fans, so I don’t know for sure. The specifications equal or better competitors and they certainly do they job. See performance tests. These fans are much cheaper for Australian buyers, and I reckon the square shape looks better than the round cans on the side provided by other manufacturers.

If you’d like to do your own research, try the following links. (prices as at Dec 2016, currency conversion at A$1.00 = US$0.72). Be sure to compare fan power and cooling performance data.

jimsusa.com US$350 (varies with suppliers) =A$486 + shipping
ramcoolingsystems.com US$499 = A$693 + shipping
love-jugs.com from US$349 = A$485 + shipping
wardspartswerks.com from US$285 = $A395 + shipping

What models will the system fit?

The cooling fans hang from the horn bracket between the cylinders. The kit should fit all Evolution®, Twin cam® and Milwaukee 8® models, except those with the ignition coil located in this position.

Do you make fans for other V-twin engines?

No, sorry. This system is designed only to fit Harley Davidson® engines. You could likely modify the design to fit other applications if you want.