In an effort to better understand the vast difference between the "by the book" crowd and the "Flog it 'till it screams" crowd I went looking for some web stuff that has some credentials behind it. I'm quoting some of these sites and offering up the source info so you folks can make up your own minds about what works and what does not. It's a LONG read so don't try to swallow the whole thing at once.
The first here is a link to the Mototune USA site that is the cornerstone of the "FLOG IT" school of thinking. Note the red letter warning...
This next quote is from the Lycoming aircraft engine company. I know this isn't directly motorcycle related but it does bring up mention about loading the rings and how important that is to a proper breakin. Also mention in this quote is made about glazing and what it is. Why an aircraft document? I chose this based on the fact that aircraft engines must put out good power but above all else must last as long as possible with no power loss. Sure sounds like how we want our motorcycles to work. Read the following quote carefully as there is a lot of parallels to out motorcycle engines.
Link to the original page at the Lycoming SiteA similar description at the Cessna Pilot's Association basically parroted this same approach.... Read it here if you're interested. I found another aircraft engine rebuilding site with a procedure similar to these two as well.A new, rebuilt, or overhauled engine should receive the same start, warm-up, and preflight checks as any other engine. There are some aircraft owners and pilots who would prefer to use low power settings for cruise during the break-in period. This is not recommended. A good break-in requires that the piston rings expand sufficiently to seat with the cylinder walls during the engine break-in period. This seating of the ring with the cylinder wall will only occur when pressures inside the cylinder are great enough to cause expansion of the piston rings. Pressures in the cylinder only become great enough for a good break-in when power settings above 65% are used.
Full power for takeoff and climb during the break-in period is not harmful; it is beneficial, although engine temperatures should be monitored closely to insure that overheating does not occur. Cruise power settings above 65%, and preferably in the 70% to 75% of rated power range should be used to achieve a good engine break-in.
It should be remembered that if the new or rebuilt engine is normally aspirated (nonturbocharged), it will be necessary to cruise at the lower altitudes to obtain the required cruise power levels. Density altitudes in excess of 8000 feet (5000 feet is recommended) will not allow the engine to develop sufficient cruise power for a good break-in.
For those who still think that running the engine hard during break-in falls into the category of cruel and unusual punishment, there is one more argument for high power settings during engine break-in. The use of low power settings does not expand the piston rings enough, and a film of oil is left on the cylinder walls. The high temperatures in the combustion chamber will oxidize this oil film so that it creates a condition commonly known as glazing of the cylinder walls. When this happens, the ring break-in process stops, and excessive oil consumption frequently occurs. The bad news is that extensive glazing can only be corrected by removing the cylinders and rehoning the walls. This is expensive, and it is an expense that can be avoided by proper break in procedures.
It's interesting to note that in all three of these aircraft procedures a key point is to keep the manifold pressure high at controlled rpms in order to force the rings into the walls at high pressure. More on this at the ending.
Here's a more conservative approach as written by Gordon JenningsAnd a slightly more vigorous approach by Kevin Cameron with some quotes from Rob Muzzy.The Break-In Game
Two questions have plagued my life as a motojournalist: The first is, "I'm thinking of getting a motorcycle. What shall I buy?" Then comes the second: "How should I break in my new motorcycle?" No satisfactory answer exists for the first question, as preference in such matter is so individual. I don't know anyone well enough to choose a motorcycle for them.
Giving break-in advice is much less dangerous and it's more in my line of work. I believe I can add to the scanty information provided by most owner's manuals. These manuals typically admonish owners to keep engine speed below a certain level and/or refrain from using full throttle. They don't say why the limits are necessary, or what damage might result from non-compliance.
Fortunately for all of us, motorcycle manufacturers have done a lot to solve the special problems of parts beginning life in service. Their built-in solutions to those problems are so good your new bike's moving parts will settle into peaceful coexistence without much help from you, as speed crazed motojournalists know from long, shameful experience.
New motorcycles delivered into the unkind hands of magazine test riders get no help at all. Careful break-in for most magazine test bikes means no wide-open, red-line running until there are three digits [if that—Ed.] showing on the odometer. That is not a good procedure to follow with a new motorcycle you own and will have to repair if it breaks. But, the fact that 30-plus years of new models have survived magazine guys' abuse speaks volumes for motorcycles' quality. For the purposes of discussion, I'm going to assume you'd prefer to ease your new motorcycle through its break-in period undamaged. Your best chance of attaining this goal lies in understanding what's happening during those crucial first 500 to 1000 miles.
The tenderest of all new or newly rebuilt engine's tender points is at the scrubbing contacts between rings and cylinder bores. Actually, it's the top compression ring that gets the big load because it uses pressure on the upper cylinder for its sealing action. Gas pressure above the piston pushes the compression ring down against the bottom of its groove and out against the cylinder wall. With gas pressure in the upper cylinder at 500 pounds per square inch or even more at part throttle, the load on the oil film separating ring and cylinder wall is also 500psi. If the ring gets past the oil and into direct contact with the cylinder, friction heating will cause melting at the contact point. What happens next with plain iron rings is that a tiny bead of melted metal from the cylinder becomes welded to the ring's contact face. The bead, traveling with the ring, then picks up more metal from the cylinder until it grows too large and breaks away from the ring. Once this separation occurs, the built-up metal particle scores the piston skirt before migrating down to the crankcase, where it does more damage until captured by the oil strainer. Advances in piston ring technology remove most of the dangers from the break-in period. Today's new engines have their top rings faced with chromium or molybdenum, metals that do not readily friction-weld to an iron cylinder wall. The worst you get from a chrome- or moly-coated ring scrubbing roughness from the cast-iron cylinder bore are some small scratches.
Cast iron, of the kind used in cylinders, has a porous microstructure that readily wets with oil and then retains it fairly well. It has the further advantage of containing numerous small graphite particles, which are themselves a lubricant. Despite these favorable factors it is still necessary to finish the cylinder bore with a relatively coarse-stone hone moved up and down as it spins to make cross-hatched scratches, which hold oil on the cylinder walls and help control oil consumption.
When you're building a racing engine you can finish-hone the bores to be so smooth they don't need a breaking-in. You can't do that in street-engines, as the smooth bores would soon become polished, and a little roughness is required for oil control. The small volume of gases cross-hatching leaks past the compression ring, moves oil down to the oil ring, then blows it through the oil return holes to the crankcase. In my racing days, I attempted to raise an engine's compression ratio by heli-arc welding more aluminum to the pistons' crowns. I tested the concept on an old piston, one I carefully measured before adding metal and was gratified to find negligible distortion after the welding. Alas, when I performed the same operation on a new piston it distorted so much down at the skirt as to be utterly unusable.
On a hunch, I placed an old piston and a new one on a tray and slid them into a 500-degree F oven, leaving them in for 30 minutes. The old piston came out of the oven just as it had gone in, but the new piston was badly warped. I should have anticipated this, as complex castings and forgings like pistons end up with a lot of locked-in stresses by the time the manufacturing process is completed. A new piston's internal stresses are relaxed by heating, and if this occurs with the piston in an oven, but otherwise unrestrained, the metal squirms like mad and ends up distorted. The same piston, closely confined in a cylinder, will take on a shape much better suited to its surroundings. It is not surprising that this should be the case, as even after break-in the pistons in a running engine are a light-interference fit in their bores. Only the oil film between them and cylinders' walls prevents seizing.
Given time, your new motorcycle's pistons will adjust to life of whizzing up and down in cylinders. Heating will relax the locked-in stresses, and confinement will keep them from warping into aluminum pretzels. Repeated cycles of heating and cooling, as occur when you ride your new motorcycle and then park it for the night, work the pistons into shape, but they have to be treated with consideration while still new and nervous. If you pay heed to the advice given in your owner's manual, those pistons will settle in without having their skirts scuffed or distorted. The rings will appreciate it, too, and if you treat your new motorcycle with enough consideration to keep the pistons and rings healthy, you won't do any damage to other vulnerable bits, like bearings, gears, and cam followers. You'll avoid post-break-in engine damage by avoiding a couple of things too many riders have made habit. Do not ever, ever zing a cold engine up to high revs, as this will pound in the pistons' skirts before you can moan "engine rebuild." The other bad habit is the lengthy warm-up, which just prolongs the period in which acids condense on cold cylinder walls and eat at everything. Fire it up, ride away just be gentle with it until it's warm and ready to roar.
One last thing: Give yourself a little time to become accustomed to that new motorcycle. There's nothing more depressing than throwing your brand-new bike down the road.
Its new, its pristine, how long do you have to baby it?
By Kevin Cameron, Originally published in Sportbike 1995 Annual
Break-in is the final finishing operation in manufacturing an engine--and you, the owner of a new bike, perform it. At the factory, the bike builder hones the cylinder walls to a fine finish, grinds cams and tappets to accurate, smooth profiles, and makes co-rod journals to high standards of roundness and accuracy. but even with all this, metal surfaces remain microscopically rough, consisting of tiny peaks and valleys. When you start a new engine, these surfaces must slide over each other; wherever the peaks stick up higher than the local oil film thickness, metal hits metal, welds momentarily from the intense local pressure, and then tears away. The oil sweeps a residue of particles away, carrying them to sump and filter. Some metal is simply pushed into shape, protected by oil additives, it deforms physically rather than being welded and torn.
Throughout the engine, this process works, quickly at 1st, then more slowly as break-in proceeds. Once the high spots are knocked or pushed down, the roughness of the surfaces no longer sticks above the oil films. Piston rings have filed themselves into a fine fit to their cylinders. Bearings spin without metal-to-metal contact, on full oil films. Break-in is complete.
This process can have three possible outcomes: (1) If the break-in begins at high RPM and heavy throttle, the process may generate more heat and metal debris than the system can handle. Then the result is destruction of contact surfaces in some parts of the engine. (2) If the break-in begins at a lower energy level and builds up gradually to higher revs and throttle, the washing action of the oil will keep up with the generation of wear particles, and the surfaces will bed into each other in such a was that the oil film can carry the load. (3) The 3rd possibility is that break-in will fail-- usually as a result of such light-duty operation that parts are not loaded together forcefully enough to bed-in to one another. Rings glaze and fail to seal. The engine never delivers full power. Fortunately, this is rare where production machines are concerned.
Factory break-in procedures are designed to steer the middle course--not so vigorous as to damage surfaces, not so timid as to have no results at all. Generally, recommended break-in consists of operation at a variety of moderate speeds, alternating with no-load coasting. The idea behind this is that firm part-throttle operation for a period puts a load on bearings and other parts, forcing their surfaces together so they can polish each other to a fine fit. No-throttle coasting removes much of the load, allowing the oil system to flush away the wear particles. Gradually increasing the load (higher RPM and throttle) allows the bedding-in process to build up over time, rather than applying a possibly damaging load right at 1st.
Rob Muzzy of Kawasaki notes: 'It wont break in until you really run it hard,' noting that, 'With today's thin, low friction rings, you cant get the parts to reach each other without a good load.' He says his team breaks in its race engines in much the same manner as for the street: 30-60min of moderate operation on the dyno, just in case there are some really rough areas, followed by several pulls (that is, hard acceleration across the powerband.) He says that only by the 3rd pull does the engine begin to show its real power.
For a street machine owner, this dyno break-in translates to a period of moderate operation (Muzzy mentions 500 miles), followed by some hard acceleration. Sustained, high-speed operation is not a good idea because it provides no wash time at low load, during which the oil system can flush away any wear particles.
Once the break-in milage has elapsed, the oil and filter are changed to remove the metal-loaded oil, and the (possibly) heavily-loaded filter.
Break-in Lore and myths: You often hear something like this: 'break it in fast and it will be fast, break it in slow and it will be slow.' There is some truth here because break-in has to apply enough load to force the parts into mutual machining action. If you timidly try to break it in at very low speed and almost zero throttle, you may never force the piston rings to shave themselves into good contact with the cylinder walls. That will result in a poor seal--and a poor performance. But the 'break it in fast' part of the saying seems to imply that the faster you push during break-in, the faster your engine will be as a result. Not so. If you push too hard, too soon, the parts will score and scuff each other because the heat generated will be enough to destroy the oil film locally. A scuffed piston ring doesnt seal.
Many engine builders agree that you should not try to break in an engine on synthetic oil. If the oil film is too good, it will support even parts with extensive surface roughness. Only a small amount of local bedding-in may occur on the piston rings, in a poor fit (glazing) that improves only very slowly over time. Manufacturers of synthetic oils are almost unanimous in their insistence that this is not so, and that break-in is normal with their excellent products. But too many engineers and tuners have seen break-in either fail or take too long on synthetics for this to be the entire truth. Muzzy says that his team breaks in engines on mineral oil, and will run the fresh engine the entire first day at the track on the break-in oil, before draining and replacing with racing synthetic.
Synthetic oils are frequently chosen for racing use because low viscosities can be used that will cut friction losses by a small amount. This may be worth the trouble on the racetrack, but for street use, the choice between mineral and synthetic oils is yours. Street engines run well with mineral or synthetic oils of the reccommended viscosity.
Your more important decision will be to follow a reasonable break-in procedure. Treat your engine with respect for its first 500 to 1000 miles, and it'll repay you by delivering its best possible performance.
This next quote cannot be attributed to anyone or any company with any credentials but I offer it as a nice concise explanation of what a break in is doing inside your engine and the goals of a proper breakin. This one comes from the Beemer F650 forum at http://www.bmwrt.com/faq/breakin.htm . Note that this is one of the very few sources that describes HOW to run your engine and for HOW LONG to do the short bursts and roll downs often reffered to in other writeups.Oddly enough there are not a lot of articles available that have some decent credentials to back them up. For this topic I only wanted info that came from reliable sources. And speaking of reliable...What the manual attempts to get you to do, but doesn't tell you why, is to limit the amount of heat applied to the various reciprocating/rotating components for any long period of time.
You have two opposite functions to perform at break-in:
1) Apply enough pressure to the piston rings (via high-load) to have them expand and match the cylinder bore (in fact, they both wear a bit and fit each other). This also applies to valve to valve-seat interfaces and all plain bearings.
2) Avoid excessive heat that would cause distortion that will prevent these parts from mating.
So how do we do this?
Progressively take short bursts of acceleration higher and higher in the RPM range, followed by fully closed throttle deceleration.
This accomplishes both requirements.
The brief burst of acceleration loads the parts as required.
The "closed throttle" deceleration relieves this pressure, and coats the moving parts with engine oil (not so much for lubrication, but to wash away the microscopic metal particles that your engine just "machined" during the acceleration phase.
Oil is "drawn up" because, with the throttle closed, the combustion chamber is a very low pressure environment during the intake cycle as compared with the crankcase).
Understand, this is a two part process:
The "closed throttle" part is every bit as important as the "open throttle" part. Full open throttle (2-3 seconds) followed by a completely shut throttle (3-5 second).
Allow a few minutes between cycles for a thorough heat soak. Vary speed and gears (I usually start with second, and work my way up to fifth).
Avoid any constant RPM.
BMW advises not to exceed 5,000rpm for the first 600 miles.
Over at www.bikeland.org I found a lot of discussions on engine breakin procedures. Well it just happens that there area a couple of big guns over there. One is Kerry Bryant who is currently with Jardine and has been with White Bros. and SuperTrapp/Kerker as well. The other is Rob Muzzy who should not need any introduction. In amongst all the bickering that goes with any break in thread these two both quietly repeat "By the Book". I'm not sure how Muzzy's information in the Cameron article above relates to his "By the Book" advice there.
So there you have it. About the only part that everyone seems to agree on is the need for short 2 to 3 second bursts of hard throttle that does not exceed the RPM breakin limits followed with a full roll off to first load the rings and push them hard into the cylinder walls and then pull off the pressure and allow the cylinder vacumn during the coast down to draw some oil up onto the walls and past the rings. The idea being to first cut away and form the walls and rings and then quickly cool and wash away the material. And along with this MOST recomend a controlled rpm range for various ranges of kms.
So, who's right? I've never used the mototune method and frankly found it a bit harsh when reading it. But I'm also aware that the manuals all offer what sounds like a granny program for breakin. I'm going to look up the suggested breakin for my 9R and see how it fits with what we have here.