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
