V-twin Tech: The 20-Year Harley
February 8, 2007
Filed under Uncategorized
The Motor Company tends to build its motorcycles to remain in service much longer than other brands. I first learned this a couple of decades ago when I asked Harley’s then-V.P. of engineering, Mark Tuttle, why Harleys were so heavy. He said H-D knew that its motorcycles are used for 20 years or more and wanted them to last at least that long. That was a good, clear answer. Indeed, Harleys are tougher, longer wearing and generally more durable than they ever have been.
How, you might ask, does one go about getting those 20 years of service Harley builds into its bikes? The short, silly but accurate answer is: “Take care of it.” We can remove the silliness part by describing what “take care of it” means.
Wear, Corrosion and fatigue are the three main obstacles to a long service life. All three are inevitable but can be reduced or nearly eliminated. Here are some of the things you should know to get almost unlimited reliable service from of your Harley.
Wear is inevitable, but can be reduced to the point of being almost unimportant. Wear is caused when various parts rub against one another. The trick is to separate them with barriers of lubrication; as long as the metal parts do not touch one another, they shall not wear. A thin film of oil between moving parts (such as piston rings and cylinder walls) prevents the normal microscopic welding and tearing these metals experience when forcefully rubbed together without the barrier of oil.
Most engine wear occurs during startup when those piston rings and cylinders may have a too-thin film of oil to prevent high spots from rubbing and wearing. As soon as the film of oil thickens enough to separate all the parts, wear essentially stops. The oil film thickens due to its being dragged between the moving parts by its own internal friction (viscosity). In the case of plain bearings, like the bushings supporting transmission shafts or camshafts, the parts are separated after about 12 degrees of shaft rotation.
The smoother and more accurate the surfaces, the thinner the oil film can be. Improved finishes and more accurately machined parts are the main reasons today’s engines can use thinner oil. Thicker oil is needed for the rougher parts of yesterday’s Harleys. Starting with the Evo series, Harleys simply have no use for the heavy oil of yesteryear.
Oil can do its job only if it separates all the moving parts. Its thickness must be greater than the largest bump or dirt particle. If we introduce some hard particles, like sand, between two moving surfaces and those particles are larger than the oil film is thick damage shall be done. It is these too-large hard particles that account for the majority of wear in a modern engine. The trucking industry routinely expects 600,000 miles from a modern heavy diesel engine. Many get a million. The main reason for this extraordinary service life is improved filtration. Cleaner air and cleaner oil greatly extend engine life.
Corrosion is the greatest enemy of the outside of any motorcycle, and atmospheric oxygen is the most plentiful corroding agent. It corrodes paint, tires, aluminum, plastic and so on. Oxygen must be kept away from as much of your bike as is possible or practical. This is accomplished with various barrier materials.
Paint is the most plentiful barrier material. The main engineering purpose of your bike’s paint is to protect the metal from attack by oxygen. Of course, if the paint job is attractive, one might be more likely to buy the bike – but that is marketing and we are over here in engineering right now.
Harley has made great strides with its paint. When I asked Mark that question at the top of the page, Harley’s paint was not so durable. It would flake off parts of the frame that might flex a bit or where the welds had not been cleaned enough. Today’s paint and powder coating are exceedingly tough.
All the bolts, washers and nuts are plated with metals that are much more resistant to oxidizing attack than the steel from which they are fabricated. Most Harley bolts are zinc plated. Zinc does oxidize slowly and the grey layer of zinc oxide that forms on the surface greatly slows further corrosion. If you polish the grey film off various bolts to restore their original luster, you remove the protective layer of zinc oxide. Do this enough times and you shall polish through to steel and create a more serious corrosion problem.
Many moons ago Harley’s had no chrome, just paint and some plating. We motorcycle types like chrome so Harley put some on. Chrome corrodes very slowly but, because of how it is applied, tends to be porous. If it were not for the layers of copper and nickel under the chrome, the pores in the chrome would allow rapid rusting. We have all seen pitted chrome from when some of those pores reach the steel and allow oxidation. Good chrome is chrome with plenty of copper and nickel under it; however, even good chrome has some porosity and needs further protection.
There are other chemicals that corrode or accelerate the corrosion of the various parts of our Harleys. We all know about salt. It absorbs water which then pumps atmospheric oxygen to the surface to which the salt crystals are attached, such as a hot aluminum primary cover.
What You Can Do
Clean and wax everything but the tire treads. That bit of porosity here and there on the chromed surfaces can be plugged with wax. The salt you collect during a day’s ride by the sea is kept away from the paint, chrome and aluminum by wax. Of course you should rinse ‘er down with water at the end of such a ride.
Any wax is better than no wax. I remember “Hollywood Harv,” a fellow mechanic who would, once each week, wash his bike and then spray it with Pledge from one end to the other. After wiping, that bike would shine like a new penny. By the end of the following week it would be a bit dirty and the wax surface would begin to have a multi-color shine like a soap bubble. But, it only took him a half-hour to bring back his new penny. Never saw any corrosion on that bike and he often rode by the beach.
An additional benefit to washing and waxing is that it gives you a chance to take a close look at your bike. You just might catch something that needs attention before it catches you – if you follow my meaning.
Lubricate everything that moves. A drop of oil or bit of grease reduces or prevents wear between the parts of folding foot pegs, levers and their pivots and even the elements of the ignition switch. Re-lube everything with each oil change.
Care of the inside starts on the outside. Before removing an oil dip stick, the oil filter or air cleaner, wipe and wash away the dirt that has collected around the edges. I have witnessed owners removing dip sticks caked with sand! Harley engines are very sensitive to particles of dirt. They run almost completely on ball and roller bearings, and such bearings have no tolerance for particles of dirt.
Use synthetic oil for everything. It is much, much tougher and does not wear out, practically speaking. It also tolerates high temperatures much better than traditional oils. It can last a long time; I normally use it for 10,000 miles.
Use the latest Harley oil filters or a guaranteed equivalent. These newer filters remove very small particles and can do much to extend the wear life of your engine. Be very careful about air filters. The stock filters or K&N replacements filters are very effective. Should you fit an aftermarket filter, I recommend that it have a K&N filter element. The foam filters simply do not remove small-enough dirt particles.
Materials wear internally when they are flexed repeatedly, some quicker than others. Aluminum will develop fatigue cracks fully ten-times quicker than steel. The farther, more forcefully and the more often a part is flexed the sooner it fails.
Your Harley has been very completely designed, tested and developed to reduce fatigue wear to an absolute minimum (remember, 20 years is the goal). You take full advantage of all that work by The Motor Company by staying within the limits assigned by Harley. Don’t over-rev the engine. Use the clutch to shift and close the throttle when you do. Don’t slip the clutch. Don’t enter a motocross race. Well – you get the idea.
Our Harleys are precious things. Each one represents more than 100 years of motorcycle manufacturing and owner experience. They have been designed to last and to be so reliable that they can be considered investments rather than disposable vehicles. Whether or not your particular Hogly-Davidson meets the standard of service and reliability is mostly up to you. All you have to do is just Take Care of it.