Most riders believe that to get the most out of their bike, they need to operate it with great care. This is true, however it must also be understood what great care actually means to the engine during the break-in procedure.
Have you ever noticed that many magazine tests show bikes that make 2-4% more power than many consumers’ bikes or cars? Have you ever noticed that many dealer’s demo bikes run very well? Do you know why? Do you want to? It sure isn’t because these bikes are “ringers” that are built special – despite the old wives’ tales.
Over the years, many things have changed. Clearances have decreased, machined tolerances have improved, operating temps have increased, materials have improved, fuels have more and more junk in them (and lubricate less), and oils have improved greatly. But the motorcycle factories still recommend the same easy break-in procedures, and oil change intervals. WHY?
Go one step further and ask why the manufacturers of piston engines for light aircraft recommend a more aggressive break-in procedure involving more load, oil changes, and heat cycles than motorcycle manufacturers do. These are engines that are closely monitored and where reliability is a matter of life and death. Google "Lycoming" and "break-in" for yourself.
I am a big proponent to aggressive break-in using load and heat-cycles, and frequent oil changes. This is the result of break-in on many new engines – some of which I have built myself, and tested the methods. I have seen the different results too many times to ignore.
There are 3 factors that make up a good break-in. Ring seal, frequent oil changes, and heat cycles.
1.) Ring seal:
If the engine is machined and assembled correctly (and running a good oil) the only parts you need to wear-in or run-in are the rings and bores. Bearings (aluminum, Babbitt, roller, ball, etc.) do not wear in. If you have ever seen inside a freshly machined and assembled engine, you will see that the bores are purposely left with very light honing marks. This is to retain oil and help cut the face of the rings to match the bore wall shape, and make the ring seal best.
If the rings are not seated properly early in their life, they will not ever do so. Once the bore roughness is worn off (in the first couple of hundred miles), there is nothing left to cut the ring faces. In extreme cases, the bores can actually glaze (filling in the hone marks) and prevent the rings from sealing. This is especially so on hard Nikasil bores using harder ring coatings than used on steel bores.
If you have ever held a set of piston rings in your hand, then you know they are like springs. However, the spring pressure is not enough to hold the ring face flat against the bore without some help. It is the combustion pressure that helps hold the ring face flat against the bore wall. If the combustion pressure is too low, the ring will roll up and down in the ring groove, and roll the top and bottom edges - reducing the already small surface of the ring face.
It is engine load that increases the combustion pressures and forces the ring against the bore wall. Light loads cause less pressure and less surface pressure between the ring and cylinder wall.
Leak down percent in the chamber and blow-by into the crankcase are the only way to measure the ring seal. This is why many engine builders also measure crankcase pressure closely during break in. I have seen several engine builders tear down new engines that did not seal up correctly and then hone and replace rings in order to get their required leak down target percentage. As ring seal is improved, each 1/2 percent becomes a greater and greater issue.
2.) Frequent oil changes:
The rough surfaces of the bores and rings break off and are either blown out with the exhaust (by coasting down), or collect in the oil. The surfaces of the gear faces in the transmission and on the balance shaft also wear in in the first 1000-1500 miles. If the oil is not changed frequently during break-in, these metallic particles can collect and embed in the softer surfaces in the engine causing premature wear of these surfaces. If you have never looked at the metallic debris in the oil of a new bike engine with only 20 miles on it, you would be shocked. Getting and keeping this debris out of the engine is very important.
Changing the oil prior to each heat cycle should be considered a good idea.
3.) Heat cycles:
A cold engine and the same one when hot, will measure differently – especially the bores. As the engine heats up, the bores grow and distort. The pistons do the same. If you heat cycle the engine frequently during break-in, the pistons, rings, and bores will correctly wear to match each other, and the block, heads, etc. eventually become "seasoned", distorting less. This may be the single most important aspect of a good break-in technique.
Heat cycling requires that the engine be brought up to operating temperature, loaded, and then allowed to cool completely. At no time should the engine temperature exceed normal operating temperatures.
A good break-in:
There is no reason to rev the engine to the rev-limiter, and plenty of reason not to do so. The peak filling of the engine occurs at peak torque rpm. Turning the engine a bit over this rpm and letting it coast down will force the rings against the walls best, and suck much of the metallic particles from the bores and rings out of the engine. Varying the rpm and amount of throttle for each successive pull gives good results.
Using mineral oil with frequent changes while loading the rings during break-in produces a better seal than factory recommendations by NOT protecting the bores as well as synthetic oils will do. This improved ring seal makes more power and lives longer as well. This has been proven repeatedly by many engine builders of all types from F1 racing to Caterpillar diesels. Once the engine has sealed up, using good synthetic oil will protect from wear best.
Poor ring seal allows oil into the combustion chamber, carbon to form in the chamber, on the sides of the pistons, and in and around the ring grooves, unburned fuel and air will be blown passed the rings into the crankcase - diluting the oil and increasing crank case pressures. None of this is good for power or engine life.
The vast majority of wear in an engine is at the top of the cylinder bores. This is where the piston ring changes direction, and there is little oil to lubricate the bore walls, but the combustion heat is the most extreme. When the piston is at the top of the bore, the cylinder pressure during combustion is the highest. Any air and fuel leaking passed the rings here because of poor ring seal or ring flutter will burn oil under the rings and dilute the oil with fuel and carbon. This causes premature wear in all parts of the engine, and reduces power and efficiency in an ever increasing manner as oil is blown passed the rings more and more frequently and produces more and more carbon in the engine.
Most engines are at the end of their life when the ring seal is reduced to a given point. If you seat the rings better to begin with, and this seal prevents carbon from wearing the engine during its life, the engine lives considerably longer.
All of this can be seen and proven by testing compression, leak down, blow-by, and oil analysis.
The drive-train responds the same way. Even ground gear faces need to see load to bed/wear in correctly. Frequent oil changes are even more important here. A magnet on the oil filter helps tremendously.
If you cannot measure leak down, run the engine hard on mineral oil and change it frequently for the first 1000 miles (the first 200 miles are critical). Then add good synthetic oil and enjoy it for a long time.
I have seen engines that are broken in correctly easily make 2-4% more power compared to engines that are broken in lightly and quite never seal up – even more compared to engines that have glazed bores. While 2-4% may not sound like much, on a 125 horsepower engine, this can mean 2.5 to 5 horsepower. Compare that to what you would pay for a bolt-on part that makes the same amount of power. Bikes that I have broken-in on the dyno have shown even greater gains, and these same engines also last longer, and use less fuel and oil.
You only get one chance to break-in a new engine. Make sure you do it with great care.
-POWER-TRIPP Performance
