Help For Hot Bikes

HELP FOR HOT BIKES

Comparing and Evaluating Oil Coolers for Street and Dirt Bikes.

Heat is what makes an engine operate, whether it’s a motorcycle engine, steam engine or nuclear power plant. Heat—if there’s too much of it—is also the biggest enemy your motorcycle engine has.

The folks who design motorcycles know all about heat. They know how much heat a motorcycle can make and how much heat a motorcycle can take. And sometimes a motorcycle can make more heat than it can take. There are ways to reduce motorcycle heat. For a motorcyclist, there are two ways: get off the gas or cool the oil. Whether you need to cool your oil or not is an important question.

Why Is There Oil?

Lubrication, the obvious purpose, really is only one of four important functions of oil. Oil cleanses an engine by picking up unwanteds such as water, acids and small particles. Oil cools an engine by transferring heat from high temperature spots such as cylinder walls and carrying the heat to a crankcase or oil tank where it can dissipate. Oil also acts as a protective coating inside an engine.

Too much heat can interfere with the oil’s ability to perform all its duties.

To lubricate, a thin film of oil must exist between sliding or rotating surfaces. Without the oil film, metal sliding on metal creates friction which creates heatenough heat, and metal can be welded to metal . . . which is what happens when an engine has a spun bearing. Sometimes momentary scuffing will occur when the oil film doesn’t exist, for instance during start up. Even slight bearing damage, however, will increase friction, cause more heat and eventually will shorten engine life.

Metal parts working against each other continually deposit small particles, the results of wear. The most common contamination of oil. however, is from blow-by gasses. Water vapor and unburned fuel are fed into the oil system from blow-by. The unburned fuel, when combined with the water vapor, forms acids. When the byproducts don’t combine, the water can rust ferrous metal parts and the unburned fuel can dilute oil and interfere with lubrication. So oil must be able to absorb dirt, water and acid. Besides absorbing unwanteds, oil coats the inside of the engine to minimize rust on ferrous metals and other corrosion on other metals. Even though aluminum motorcycle engines can't rust, they can corrode and aluminum oxide is much more abrasive than iron oxide.

Finally, oil must carry away excess heat from lubricated surfaces. On air cooled engines, oil is the most important cooling system, becoming an ersatz liquid cooling system but without separate pumps, hoses and radiators.

Oil Temperatures

High temperature isn’t the only problem for oil. Low temperatures can cause problems too. When oil is heated, it tends to flow easier or get thinner. At low temperatures oil gets thicker or more resistant to flow. It’s called viscosity and it’s measured by different tests, using different units but always relating to an SAE viscosity number. That’s what the number of an oil can indicates. If the number is low, such as 5W or 10W, the oil is said to be thin or have a low viscosity. A high number, such as 40W or 50W is thicker or has a higher viscosity. There are reasons for both high and low viscosity oils.

In order to provide lubrication the oil must be thin enough for hydrodynamic action, that is, form a film of oil between surfaces, but thick enough to offer a continuous boundary between surfaces. Increased wear results from oil that is either too thin or too thick. Minimum wear results when oil viscosity at engine operating temperatures is 30 to 40 as measured by a Saybolt viscosimeter. Because operating temperatures change, wear rates can increase as the oil gets thinner with more heat or thicker with too little heat.

There are other problems, as well. The water vapor which oil collects should evaporate from the oil system during operation. This requires temperatures of at least 150 degrees F. Not all parts of an engine develop the same amount of heat. Places with the highest pressures, such as cam followers, develop the greatest heat and can heat small quantities of oil to temperatures much higher than the overall temperature of the oil system.

High temperatures affect oil in other ways. Even at normal operating temperatures oil gets hot and gradually breaks down. Breakdown occurs when oil combines with oxygen. Oxidation forms hard carbon and varnish deposits on engine parts. Additives in motor oil also breakdown and oxidize. Because the additives prevent corrosion, help hold particles in suspension and reduce wear, their loss is significant.

Generally, a minimum temperature of about 160 degrees, normal temperatures of 180 to 200 degrees and maximum temperature of 250 degrees F are quoted by authorities as acceptable. But not all agree. It’s a matter of priorities. And use. Above 200 degrees F, oxidization doubles for every increase of 18 degrees F. So the hotter oil gets, the faster it deteriorates.

Measuring Oil Temperature

Theory makes interesting reading, but for the motorcycle owner it’s more useful to know what’s happening within our engines, that is, do our individual machines and usage and riding habits create possible problems? Are they problems an oil cooler (or more frequent oil changes) can help to solve?

The first step is to know what temperatures are reached by the engine oil in normal service.

Before fitting coolers, we installed oil temperature gauges and used them to monitor a selection of engines (that means the bikes we had in house at the time) under a variety of conditions.

Simplest gauge of the lot, and an excellent unit for certain applications, was a dipstick thermometer made by Baja Gear. At $19.95 it’s a bargain. The unit is designed to work with any engine using a separate oil tank, i.e. Harleys, Triumphs, certain Hondas, or on engines with dipsticks. Because each stick has a specified length, Baja Gear cannot yet offer units for all such engines and is concentrating on the more numerous ones.

In our cases (chuckle) we used Baja temp-sticks on a Honda XL250, Honda CB350, Yamaha TT500 and Yamaha XT500.

Surprising. The XL250 recorded a highway temperature of 210 degrees F. A hard run through a long, deep sandwash showed a reading of 200 degrees. The owner expected the reverse, but as the engineers tell us, heat produced is a function of power produced, and it takes more power to run a steady 60-65 mph with a 250 Single than to mush through sand at 35 or 40.

The CB350 engine topped out at 200 degrees. Odd thing here was that it took 15 miles on the highway to reach operating temperature. Preliminary finding was that unless a road engine gets a longish run, and unless its operating temperature is well above that needed to cook out water vapor and acid, the engine may be running cooler than is good for it, rather than hotter.

The XT 500 was monitored while puttering about on city streets and local trails, and temperature ranged from 175 to 200, again depending on engine load.

The TT500, as we’ll see later, was ridden faster and harder and the temperatures showed it.

For more conventional motorcycling, two electric VDO-Argo gauges were used. One was mounted in a fairing on a full dress Kawasaki KZ1000 and the other was mounted on the handlebar of a Suzuki GS550, two of our long-term test bikes. The sensor for each unit is a replacement for the oil sump drain plug on the bottom of the oil sump. The gauges read from 120 to 300 degrees F. During normal use the VDO gauges worked fine. When the 550 was track tested, however, the needle came loose on the gauge. Whether it was caused by high vibration, high temperature readings or simply a factory defect, we don’t know. The other gauge encountered no problems. The handlebar mount unit costs $49.95, the fairing mount $45.95.

For precise measurement during the comparative tests, two digital thermometers were used. Kendick Engineering provided a unit for the KZ1000 and Hayden Trans Coolers loaned one for the Suzuki. The Kendick thermometer operated off a sump-mounted sender while the thermometer on the Suzuki operated off'a sender mounted in an oil gallery behind the cylinders on the top of the crankcase. Oil pressure gauges were mounted on both the GS550 and Kawasaki.

The Tests

The Suzuki, when ridden around town, takes about 10 miles of riding to stabilize oil temperature. In air temperatures of 80 to 90 degrees F oil temperatures of 180 to 200 degrees F were common. Sustained freeway travel would raise temperatures to 210 degrees F with 10 degree variations depending on traffic and terrain. Brisk canyon riding, especially long uphill stretches, would raise temperatures to 235 degrees F.

To achieve hard riding in a safe, controllable test, the 550 was taken to Willow Springs Raceway near Lancaster, California. Test day was cooler than normal with a range from 70 to 80 degrees. The 2.5 mile racetrack climbs up a hill with swift sweepers, tight turns and enough straights for speed. With the basically stock GS550, superbike production racer Pat Eagan was lapping consistent 1:49s and 1:50s for a respectable 82.57 mph average. After each oil cooler was installed, the Suzuki was ridden moderately until oil temperature stabilized at 200 degrees F. Then came eight hot laps. Temperature readings were made on the second, fourth, sixth and eighth laps. Peak temperatures without any oil cooler were 239, 258, 268 and 272 degrees F. Oil pressure dropped from 1.5 to 1.2, 1.15 and finally 1.1 pounds per square inch at 3000 rpm. Factory specifications are for a minimum of 1.4 psi. At 200 degrees F oil pressure was a healthy 1.9 psi.

Even with 20-50 Bel-Ray racing oil the pressure had dropped critically. Had a single viscosity 30 or 40 weight oil been used oil pressure could have been lower still. For this use, an oil cooler would be worthwhile, if it would provide any appreciable cooling.

To simulate a heavy touring load the KZ1000 was loaded with saddlebags, rear scoot boot, fairing, two 160 lb. riders and then another 50 lbs. of cargo in the saddle bags. Then the motorcycle was ridden 12 miles up a mountain pass with an elevation change of 4000 feet while the passenger,> pencil and clipboard in hand, recorded temperatures at every mile. Again, air temperature was lower than expected at 80 degrees F but temperature was consistent throughout the day, never varying more than two degrees up or down.

Each run was begun at the bottom of the hill with the oil at 180 degrees F. Oil temperature climbed steadily as the Kawasaki ran up the grade at 60 mph. By the time the bike reached the summit, oil temperature was 234 degrees F. Oil pressure dropped from 3 psi at 4000 rpm at the base of the grade to 2 psi halfway up each run. Factory specifications call for 2.8 psi at 140 degrees F. Oil pressure was considered safe during the tests.

Under ordinary freeway cruising in 70 degree F air. the Kawasaki would run at 180 degrees F. When air temperature was 100 degrees F and speed increased to a normal Southern California freeway pace of 65-70 mph the oil temperature increased to 210 degrees F. Had the touring test been performed on a hot day or with the bike towing a trailer, an increasingly common touring load, there would have been a definite need for greater cooling capacity. If a touring bike such as the Kawasaki is not generally used under more difficult conditions than the CYCLE WORLD test and the oil is changed frequently there would be a less clear cut case for greater oil cooling.

A final test involved a Yamaha TT500. The test site was a six mile long stretch of sand north of Adelanto. California named Playground Sandwash. For the first two miles it is flat, straight, wide and allows wide-open running. In the next three miles the wash starts a gradual climb and loses most of its straightness but remains a very fast stretch. The final mile is a killer. It's slow, tight, twisty and treacherous—especially if you're pushing yourself and a 275 lb. bike to the limit. At the top the bike made a quick reverse turn and the run was made in reverse for a total of 12 miles in all.

Because of the difficulty of the ride, constant observation wasn’t possible. Instead. the run was started with the engine oil at 175 degrees F. the oil temperature was checked by the rider at the halfway point, at the turn around and at the end of the run. Without a cooler the TT500 reached a temperature of slightly over 275 degrees F at the mid-point and was at 260 degrees F at the end of the loop.

Manufacturer: Kawasaki Accessory Application: KZ1000 Price: $69.90 Comments: Cooler is $59.95; adapter kit is $9.95

By a few degrees, the thumper’s oil reached the highest temperature of any bike tested. One reason was the higher 90 degree plus temperatures on test day. Another reason was the, ah, aggressive riding of CYCLE WORLD’S test editor, Ron Griewe. But even with a slower novice rider the Yamaha produced oil temperatures of 240 degrees F. An effective oil cooler would be a definite aide for a big four-stroke desert bike.

The Coolers

Six companies provided oil coolers for testing. Derale, Lockhart, Hayden, Kerker, Halo and Kawasaki offered coolers to fit the KZ1000. For the Suzuki, the Derale. Lockhart, Hayden and universal Halo coolers were fitted. Only Derale and the Halo were available for the Yamaha.

Because the oil lines for most of the coolers are the same, the Lockhart fittings were used for all but one of the coolers fitted to the Kawasaki. On the Suzuki Hayden fittings were used on the Hayden and Halo coolers. Derale fittings were used on the Derale and the Lockhart used its own full-flow fittings. With the full-flow system, all oil leaving the oil pump runs through the cooler. The other coolers use a bypass connection which routes only part of the oil through the cooler. On the Yamaha the Derale fittings were used for both coolers. The Kerker cooler on the Kawasaki uses its own braided steel lines and a thermostatic bypass valve.

Installation, for the most part, is simple and instructions adequate. There was a problem with the fairing-equipped Kawasaki. The mounting bracket for the Vesco fairing interfered slightly with mounting of all the coolers. Minor changes in mounting allowed all the coolers to fit, however. On an un-faired Kawasaki all the coolers fit without problem. On a Kawasaki with a Vetter-made Kawasaki fairing, only the Kawasaki cooler would fit without problems. >

Manufacturer: Hayden Application: GS550 Price: $82.30

Manufacturer: Derale Application: TT500 Price: $44.00 Comments: Stock oil lines must be cut, and used for cooler installation.

Results

Two of the coolers mounted on the Kawasaki, the Hayden and Kerker, provided the greatest temperature decrease, about 15 degrees F. The Lockhart and Kawasaki coolers dropped maximum temperatures about 10 degrees F. The Derale dropped temperatures up to 7 degrees F while the Halo actually increased temperatures up to 5 degrees F during most of the run but dropped maximum temperatures 1 degree F. Because the Halo incorporates a filter and appears designed more for radiating heat than conducting heat away, it did little to lower temperatures of the large Kawasaki.

Two factors limited the temperature reductions on the Kawasaki. One, the engine

is large and has a large heat generating capacity. Consequently, the Kawasaki engine is designed to dissipate a large amount of heat and has a large oil supply. The oil coolers added a small amount of cooling when compared to the cooling ability of the standard engine. And because the oil temperatures were lower to begin with than the other motorcycles, there was less excess heat to dissipate.

All of the oil coolers provided better results on the Suzuki. Most effective was the Lockhart, which reduced temperatures 39 degrees F at the maximum. The Hayden was nearly as effective, reducing peak temperatures 37 degrees F but not reducing mid-range temperatures as much as the Lockhart. Next in line was the Derale which reduced peak temperatures 26 degrees and provided a respectable 20 degree F difference during most of the runs. Even the Halo provided a minimum of 6 degrees F cooling on the first lap and a maximum of 15 degrees F for the next four laps.

Surprisingly, the Derale and the Halo coolers provided almost the same results on the TT500. Both coolers reduced temperatures 20 degrees at the final check to 240 degrees F and temperatures never exceeded 250 degrees with either cooler. The rider noted, however, that temperature increase may have been slightly less with the Halo than the Derale. The Halo also is particularly well suited to off-road use because its design should be less affected by rocks or other flying matter.

Manufacturer: Halo Application: Universal Price: $39.93

Comments: Incorporates paper filter with ceramic magnet to trap ferrous particles. Consumer must purchase or fabricate his own adapters for installation.

Cold Weather Alternatives

All the tests involved hot weather riding and demanding conditions. But many bikes which will occasionally be used at high speed will be used in cold weather and for commuting, too. Reducing oil temperature can interfere with necessary evaporation of moisture from the oil and can actually cause problems. Harley-Davidson equips the Low Rider with an oil cooler but supplies a vinyl cover for the cooler to prevent excessive cooling in cold weather. Cooler covers are simple to make and can help.

Two companies currently produce thermostatically controlled bypass valves for oil coolers. Patsu Corporation offers its Kooler Kontrol for $29.95 from Kerker Engineering and Lockhart sells the BP-180 Thermostat for the same price. Both units operate similarly, rerouting oil from the engine back to the sump when oil is cool and allowing the oil to flow through the coolers when warm.

Conclusions

Not every motorcycle needs an oil cooler. Whether your bike needs a cooler or not depends on the use it receives. Only you can decide. The best way to find out if you need a cooler is to install an oil temperature gauge. If oil temperatures regularly exceed 250 degrees F, an oil cooler may help both your engine and your oil last longer.

If your motorcycle occasionally exceeds 250 degrees F, the choice isn’t as clear. Changing oil more frequently is an alternative to cooling the oil. That’s also a better answer if most of your motorcycling is short trip commuting which builds up the moisture content of your oil.

Almost all motor oil available today is tested to withstand temperatures of 300 degrees F for 60 hours of use. Occasional high temperatures will likely be more damaging to a motorcycle engine than to the oil. Some oil. such as synthetic lubricants, are designed for even higher temperatures and won’t breakdown at temperatures up to 400 degrees F. That’s another alternative. >

Manufacturer: Kerker Application: KZ1000 Price: see below Approx, prices: Complete standard kit $69.96

Braided line kit $29.95 Kooler Kontrol $29.95 Total as tested: $130.00

Manufacturer: Lockhart Application: GS550 Price: $69.95

Comments: Only full-flow system available for GS550 application.