Engine Break-in: Truth, Lies, and What You Really Need to Know.


grayracer513

The process of breaking in, or “running in” a new engine is a subject that has much more controversy surrounding it than it probably should.  It is steeped in old rumor, myth, hard fact, and half-truths, with a healthy blending of real science and pure BS.  Part of the reason for this jumble of fact and fiction is that the technology at the core of the internal combustion engine has evolved so much in just the past 70 years, and another part is that there is within the engine itself a kind of conflict of interest regarding the needs of various sub-assemblies as they are first put into service.

One school of thought is that the engine needs to be treated gingerly for the first little bit of run time.  Another camp insists that if it isn’t subjected to heavy loads very early on, it will sacrifice part of its performance potential.

The fact is that, like a lot of things, there is some truth in most break in philosophies, and the empirical record is full of folks who followed any of several approaches and were successful, ending up with long engine life and extended performance in spite of the advice of the proponents of alternate methods. Why?  Let’s examine the issue.
 

What is “Break In” in the First Place?

In any machine, when there are two freshly machined parts that move against each other, there is a basic problem of preventing them from damaging each other due to too much friction under too much force.  Obviously, this is why the machine uses some form of lubrication at such points of contact.  In fact, the fundamental goal of lubrication is actually to completely prevent the two surfaces having any direct contact whatsoever.  

There two basic states, or modes, of lubrication.  These are “hydrodynamic”, wherein the moving parts glide over each other totally separated so that they “plane” on the oil like a skim board, and “boundary”, wherein the two parts have forced their way past the oil film and have come into actual physical contact.  “Anti-wear” additives are added to the oil to prevent damage during boundary conditions.  More in this in a minute.

Next, there is the fact that even the most perfectly machined surface is never perfectly smooth.  When looked at under a microscope, “asperities”, which are craggy looking high and low spots resembling a mountainous landscape, can be seen.  If two such surfaces are moved across one another, the high spots of one dip into the low spots of the other, creating friction.  This naturally has a tendency for the two parts to knock the high spots off of each other in the process known as wear.  The unwelcome byproduct of this process is the debris that results from knocking down all those high spots, which is the major reason break in oil needs to be changed sooner than normal.

With that in mind, the basic goal of running in an engine is to minimize this wear process while promoting a kind of polish between the two moving surfaces, which then reduces the operating friction, makes hydrodynamic lubrication easier to achieve, and extends the useful service life of the assembly.  Make sense?
 

Conflict of interests

As mentioned earlier, different kinds of moving components operate differently, are subject to different kinds of stresses, and have different needs during break in because of that.

“Plain bearing” surfaces like bushings, the bearing inserts on common automotive crankshafts, piston skirts, and the camshafts in typical motorcycle cylinder heads, need to be kept well apart from one another initially until they can develop that high degree of polished compatibility mentioned above. One means of helping this process along are “boundary lubricants”, the anti-wear compounds I spoke of.  These are usually metallic compounds of zinc, phosphorus, molybdenum, sulfur, etc., whose purpose is to become embedded in the low asperities of the metal surfaces so as to prevent the neighboring high spots from digging into them.  This takes place by running the oil parts together under moderate pressures with a film of oil containing these compounds for a period of time long enough to allow it to take place.  Once accomplished, the surface is in effect, “flatter”, which supports the oil film better, improving hydrodynamic lubricity, and the two parts can bear on one another with very high pressures without significant wear taking place, even under “mixed film” conditions where the oil is beginning to fail to separate them.  There are two major advantages in this process.  First, it reduces the amount of actual wear required to produce a good polish, and that reduces the amount of debris generated during break in.  The second is that these boundary lubricants can now permanently protect the moving components against damage at times when lubrication is marginal, such as during startup, or when the stays running while the bike lays on it side after a fall.

camshaft.png
Image Courtesy of DIY Moto Fix

 

Another hazard is “adhesive wear”, which is the transfer of metal from one part to the other.  This is seen as a “smearing” of metal from the bearing or piston skirt surface onto the shaft or bore surface it runs against, and from the standpoint of break in, is the result of too much pressure applied to the parts before an adequate amount of the boundary lube additives become embedded in the surface of the parts.  It usually always involves the softer of the two metals being transferred to the harder.

Ball and rolling element bearings don’t break in in this way because their components don’t slide over each other as plain surfaces do, but they still depend on hydrodynamic separation, and on the embedding of anti-wear compounds into their contact surfaces.  They take considerably less time to receive a viable level of boundary protection, though, and can survive nicely on remarkably little hydrodynamic lubrication after a very short run in period.

Then there are the piston rings.  This is a major conflict area, since they do need to be protected from excessive localized wear and adhesive damage, but at the same time, their primary job is to form an effective seal against the walls of the cylinder bore.  Therefore, they have to have a particular balance of anti-wear protection together with enough actual wear to produce a nearly complete match to the shape of the bore in which they run.

So, with that understood, what exactly is the answer to the question of how to properly break in a new or freshly built engine?
 

Old realities

In the world of engines that was, it was normally the accepted practice to run the engine for a significant distance at not much more than half its potential output.  This was true for a number of reasons, one of which was lubrication technology.  Highly effective anti-wear compounds such as those currently available didn’t exist in the early fifties and prior, so the process of polishing off the asperities without wreaking havoc on the bearing surfaces had to be approached somewhat more cautiously, and given enough time to take place without the benefit of the filling in process modern phosphorus and moly compounds provide.  Now that those additives are available, and generally included in premium motor oils, break-in periods spanning thousands of miles or scores of hours are no longer needed.

Add to that the fact that modern metallurgy and manufacturing methods are now capable of producing much more accurately machined parts that fit together almost perfectly out of the box, and there is much less wearing in necessary in the first place.  Twenty years ago, the idea that there would be one size cylinder and one size piston made for an engine, and they would always fit together with the specified clearance range would be considered impossible.  Now it’s standard operating procedure for several models including high performance engines.
 

Old myths

One of the persistent myths surround the break in process is that synthetic oils can’t be used during the period.  This may have been true 50 years ago, but not any more, and perhaps not even back then.  The myth is centered on the notion that synthetic oil lubricates so much better than conventional oil that none of the wear required to polish and match things up will take place quickly enough, and that in particular, the piston rings will not wear into a good match to the bore fast enough.  If the rings take too long to seal, the story goes, they will build up a glaze from the combustion gasses blowing past the incomplete seal.

One part of this is true; if the rings don’t seat fast enough, they can actually develop a coating of partially burned fuel byproducts, and that will prevent them from ever being close to 100% effective in sealing the force of combustion up in the combustion chamber where it belongs.  However, really significant advances in piston ring technology have all but eliminated this problem.  More on that in a bit.

The two parts that aren’t true are one, that synthetic oil lubes better, and two, that too much lube during break in is a bad thing.  Synthetic oil is almost always the same basic chemical compound that conventional oil is at its base. The difference is just that instead of being dug out of the ground and having a bunch of undesirable stuff removed from it in the refining process, it’s created from scratch in a lab, with none of the bad stuff included.  And in fact, while Group IV and Group V synthetics are completely lab created, the so-called “synthetic” Group III oils are conventional oils that have undergone a higher level of refinement than other conventionals, and are allowed to use that term.  So there really isn’t a difference in them in terms of their ability to keep two metal parts separate from each other, only in their durability under severe conditions.  Frankly, the only sensible reason not to use them during break in is that they tend to be more expensive, and break in oil should be changed after a much shorter interval because the break in process normally produces a lot more debris than will be present after the process is completed.

Even if it were true that they lubed better, that would actually argue in favor of their use.  Remember that the wear surfaces of new parts are rougher than we want them to end up being, which creates undesirable friction and more wear than we’re looking for.  Good lubrication is more critical during break in than at any other time, so the use of a high quality lubricant is extremely important.

And whether it’s synthetic or not, the use of an oil containing a lot of anti-wear additives is critical during break in because of how important the embedding of the new parts with those additives is to the entire process.
 

What about the rings?

Ah, yes, the piston rings.  Back in the medieval times of the 1950’s, piston rings were almost universally made from simple cast iron.  The process of machining both the rings and the cylinder bores was much less accurate than is currently standard, and they required a fairly significant amount of time to wear in to a good fit with the bore.  Newly machined bores at the time were considered passably round if their radius varied by less than .0015”, while modern standards are about half that.  Rings could not always be expected to be perfectly round once compressed to the bore diameter, either, which produced uneven pressures around their circumference, and uneven sealing to go with it.  This was actually made worse by the introduction of chrome faced compression rings, which were brought into common use as a means of extending the wear life of the rings so they didn’t require the undesirably frequent replacement that iron rings did.  However, the greater resistance to wear also extended the break in period, the time between installation and the development of a complete seal.  Because of that, chrome rings were actually very much subject to becoming glazed over by combustion byproducts, and that was indeed a real problem.

DIY Moto Fix 2.png
Image Courtesy of DIY Moto Fix

The modern solution was to machine a shallow hollow face into the top ring and fill it with a hard compound of molybdenum.  This served two functions; it reduced ring friction, and provided a small amount of sacrificial wear to the ring face that both sped up the “seating” process of the ring, and also protected the bore from wear by depositing the moly compound onto the bore walls, filling in the asperities there with what amounts to an anti-wear coating.

Another benefit of this is found in the fact that since the top, moly-filled ring seats and seals so much faster, almost immediately, in fact, that it protects the second compression ring under it from as much exposure to combustion gasses as it would otherwise get well enough to allow the use of a long-wearing chrome ring without the associated problems of glazing while wearing in.

Combine all that with current machining practices that produce rings and bores that come off the machine almost perfectly round and in matching sizes, and there’s not very much wear even necessary to seat them.
 

Balance

So with all of that having been said, the ideal break in process for a new or completely rebuilt engine is a matter of achieving a kind of balance of causing wear where it’s desirable, and preventing it where it isn’t.  Ball and roller bearings don’t need to be dealt with very cautiously, but plain bearings need some respect and gentle treatment.  The rings need some force applied.

One popular school of thought is that the engine should be warmed up fairly judiciously to at or near normal operating temperatures, and then placed under heavy loads of at least 85% of the engine’s potential output as soon as practical in order to seat the rings.  This method will in fact usually produce a good ring seal that will last a long time, but it carries obvious hazards to any plain bearing surface, including, most importantly, the piston skirt.

Another even more hazardous common practice is “dry building” the top end, wherein the piston and cylinder are not lubricated at all during assembly.  The concept is supposed to encourage a more complete seal of the rings by encouraging them to wear quickly, before they have a chance to have any oil glaze onto their faces.  On the one hand, this is just a little bit like kidding one’s self, because oil thrown off from the connecting rod bearing in a four stroke will hit the bore walls within 10 seconds of startup at most, in a four stroke, and in a two stroke, the incoming fuel/oil mix will contact the piston and bore below the ring grooves before it ever gets to the top end for the first time.

One thing that is avoided by dry building is an excess of oil behind the rings in the ring grooves that may cook down into a sludgy deposit and interfere with their ability to float freely in the grooves as the piston moves around in the bore slightly, but that can be avoided simply by not slopping the rings up to an excess.
 

So, then, how to proceed?

The ideal method of breaking in a top end is “dead running” the engine for a short time.  The rotating assemblies should be lubed with an appropriate, reasonably generous amount of the same oil that will be used in operation.  In a four stroke, the camshafts should be left out of the assembly altogether for this phase when practical.  The piston is lubed only at the wrist pin, and the bore and rings are left dry.  Then engine is then rotated by any convenient means, including the electric starter, if so equipped, for between 150 to 300 revolutions.  On smaller singles, one can put the bike in gear and rotate the rear wheel by hand, or walk the bike around in gear.  This will almost completely seat a moly filled top ring and coat the bore in the ring sweep area without placing any undue stress on the piston skirt.  A dry moly powder product made for this precise purpose, such as Total Seal’s Quick Seat dry film lube, is a good thing to use in this step. Dust the rings with a little and wipe some on the bore.

After the dead run, remove the cylinder and place one or two drops of oil on each ring, rotate it in its groove to distribute it, and wipe away any oily excess from the ring lands of the piston (the area between and immediately above and below the rings).  Wet your fingers with oil and wipe a film onto the bore walls, again wiping away any oil that is more than just a film, and reassemble the top end.  In real life, the compression rings of a four-stroke are lubed only by gasoline. The assembly lube should be just enough to protect them during the first 30 seconds of their exposure to live fire.  Complete the rest of the assembly, lubricating all rotating and moving parts like camshafts, lifters, etc. with engine oil.  Moly “assembly paste” should only be used where specifically called for, and sparingly.

When it comes time to start the engine up live, pay close attention to odd noises, leaks, loose things, and verify oil pressure and delivery to the extent possible.  Give it at least 30 seconds to run up normal oil pressure and fill the passages of the lube system.  If you don’t have a good sized fan to blow over the radiators, it’s wise to hop on and ride it around fast enough to keep it from heating up too quickly.

Shut it off and let it cool a little while you double check things mechanically.  This lets it “soak “ in its own heat a little, and evens out the internal temperatures.  Then it’s time for phase two. While it’s still warm, start it up and ride at a level at least 25% of its capability, but not more than 60% for around 5 minutes, then increase that  to from 35% to 75% for another 10 minutes.  Here, you can take another brief break to recheck your work, then take it out and run it fairly hard, with cycles of acceleration and deceleration  at about 90% of it’s full potential for around 10 minutes.

At this point, shut it down, change the oil and service the filter, and call the process done.  Break in is over. Go out and ride.


Engines off the showroom floor

If you’re dealing with a brand new bike off the showroom floor instead of an engine you just went through, there’s even less to worry about.  That’s because the factories usually do the dead run on the cylinders during the assembly. Methods vary from one brand to another depending on how automated the process is, but almost all of them do it one way or another.  Then when the machine reaches the end of the line, it gets started and checked over for any problems.  The factory approach to addressing issues that turn up at this point also varies, but any bike that makes it to the dealer has been run long enough to skip the initial steps above and go right to the second phase; run it  for about the first 10-15 minutes at up to about 60-75% of its capacity, then step it up for another 10 to 15.  You want to avoid thrashing it right at first, but don’t “baby it” during the process, either.  Shut it down, look it over, and if all looks well, call it done and have at it.  

The truth is that the break in period has been reduced to a less than one hour experience by improvements in metallurgy and machining methods, improved engine oils, and proper assembly practices.  The main keys to success are to put it together right, avoid either being too hard or too easy on it at first, use a good oil during the period, and do a complete oil change early.

*********
 

About the author

Richard Ribley, (aka grayracer513) was a professional motorcycle mechanic and fabricator for 9 years, then moving on to automotive dealerships, where he specialized in engine, transmission, and powertrain overhaul and repair for over over 27 years. He is an ASE and Chevrolet Master Technician certified.  During the last 15 years he has maintained his own fleet of motorcycles and built engines and suspensions as a sideline for friends and associates.

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A veteran of the moto sales industry once told me that the "break in" period on your new bike is stated such that you do not go out and immediately kill yourself riding an unfamiliar machine....

 

Makes sense to me since most bikes get a hard run on the dyno at the factory before it hits the showroom~~

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i agree to the point of not worrying too much about a new engine, but just run it on the easy side for awhile and 'do' heat cycle it .. the factor mr qualified expert misses is parts expand and contract with heat and going out and being hard on it can make things go out of tolerance to the point of damage before theyre polished in good ... coating them with 'fantasy blend' synthetic wonder oil is a mistake to, sorry, but it is  ... and the worst idea promoted, it will take 10k miles to fully break in because 'point B' mr quailified expert misses is more than the top end on a bike is breaking in .. but really, theres nothing better to me than watching some idiot haul his brand new supersport bike into the dealer with holes blown in the pistons and everything else because he went out and did a 'hard' break-in .. its a beautiful thing actually ..

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16 hours ago, cowpie said:

i agree to the point of not worrying too much about a new engine, but just run it on the easy side for awhile and 'do' heat cycle it .. the factor mr qualified expert misses is parts expand and contract with heat and going out and being hard on it can make things go out of tolerance to the point of damage before theyre polished in good ... coating them with 'fantasy blend' synthetic wonder oil is a mistake to, sorry, but it is  ... and the worst idea promoted, it will take 10k miles to fully break in because 'point B' mr quailified expert misses is more than the top end on a bike is breaking in .. but really, theres nothing better to me than watching some idiot haul his brand new supersport bike into the dealer with holes blown in the pistons and everything else because he went out and did a 'hard' break-in .. its a beautiful thing actually ..

You had some good points, right up until you had to be a condescending jerk. You know you can share ideas and critiques without being an ass, no? Doing so is a better way to get people to listen. :thumbsup:

Edited by Twowheeladdiction
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I would be hesitant to put any oil on the ring grooves, but as the author importantly pointed out, excess oil on the ring grooves will prevent the sealing pressure from the cylinder from properly expanding the rings, and the resulting buildup will prevent the rings from ever sealing properly. I have seen that very thing before.

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On 8/7/2017 at 9:45 PM, cowpie said:

....the factor mr qualified expert misses is parts expand and contract with heat and going out and being hard on it can make things go out of tolerance to the point of damage before theyre polished in good

Expansion and contraction are calculated into the clearance specifications by the engineers, and is fully accounted for.  If you read the last few paragraphs of the article, I believe you will see that a thorough and extended warm up, including a heat soak, is recommended. This is specifically intended to moderate the warm up process to avoid problems that might possibly arise from the fact that some parts expand more rapidly than others, and to a greater degree. That problem, by the way is another issue that has been mitigated to a large degree through advances in metallurgy. 

Heat "cycling", or heating and cooling repeatedly for its own sake doesn't really accomplish anything, as it does not change the properties of the metal parts, and it causes no wear in and of itself.  Break in is a controlled, moderated wear process.  Heating and cooling just so it can be heated again doesn't contribute anything.

On 8/7/2017 at 9:45 PM, cowpie said:

'point B' mr quailified expert misses is more than the top end on a bike is breaking in ..

This makes me wonder if you read the article at all, since the wear in needs of all types of the moving components were discussed at length, including ball and rolling element bearings as used in the crank assembly, and plain surfaces such as the cam shafts, lobes, and lifters. 

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Great article!.  I'v done a LOT of research on engine-break-in... and this write-up contained information that i had NEVER heard or read before.    Good stuff.

HOWEVER.... you did miss some salient points.  One being, that a different section of the ring-face is in contact with the bore when under high load (cylinder pressure), than, when under light loads.  

Also, you didn't speak about the importance and procedure of wearing-in the other rings (on a 4 stroke). 

Edited by Marek0086
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After a decade of owning 2 different dynojet dynos and doing thousands of runs on hundreds of fresh built race engines , I can add in something that 99.9% of people will never experience..

Beyond just the experience of breaking in hundreds of engines...

My first readings of race engine break in were in published articles long ago... Written by Jack Roush and Smokey Yunick... And what they wrote had made sense intuitively , and were of similar mindset... I had adopted their methods so very long ago , had nothing but stellar results, and have had zero reason to doubt or change it..

The idea was to take advantage of the rougher initial microscopic peaks of the machined surfaces ... Let them wear... actually force them to wear and create a piece to piece self machining polish to final fit... All while the surfaces had the original "sharper peaks" ... Make them wear while they were effective at burnishing... Shave the peaks off under pressure as opposed to lower pressure operation that would let the peaks round off and permanently reduce their effectiveness , or chances of, ever achieving perfect break in or seal ... So the biggest concern for power production is the Holy Grail of "seeing if you have an engine at all" : the ring seal... Universally accepted by all engine builders is that ring seal is the bottom line of if you have a race engine, or if you don't.... Packing and lighting a fantastic charge of air fuel mix doesn't amount to much if you aren't sealing that pressure close to 100% and making that charge WORK for you... Plus the hot blowby past the compression ring is responsible for so many accelerated bad processes that the downsides of bad ring seal go exponentially beyond just power loss...

The methodology and reasoning for break in from both of the legendary endurance race engine builders sums up something like this...

Let the engine slowly warm up to operating temperature without much load at all.... Letting parts achieve their "at temp/ hot running shape" before going hard at break in ... Pistons for example are neither round nor cylindrical when cold, as their cold shape has to allow for the large heat gradient and differential expansion from combustion chamber heated top, to the bottom of heat shielded and heat sinking skirt...

So... Slow/ unloaded warm up to operating temperature.... Then the equivalent of full throttle acceleration through 2~3 gears at a time.... No extended high rpm running... But full throttle and shifting appropriately... Combustion pressure forcing rings and cylinder peaks to shave off before the round off and become dull ...

Then chopped throttle engine braking with the idea that the vacuum above the piston will assist in pulling a small amount of oil around the ring set before the next acceleration run... Lubrication / cooling/ debris washing...

Then hit it again for a 3 gear run.... In sequence for about 15 minutes... Roughly the equivalent of a 15 minute moto except for extended engine braking after each 3 gear blast...

After 15 minutes ,change the oil and filter... You're done!

Now... Back to dyno running...and the breaking in of hundreds of fresh top end race engines.... On the dyno...

Through the series of pulls , you would get to watch the effects of ring seal as power rose through each successive set of runs... Ring seal increases, power goes up... You can see on the graphs when you "have an engine"...

Bring it up to temp just lazily running the machine spinning the dyno drums...  Shut it off and let it heat soak... Run it spinning the drums again ... Then when it's warm....

Full throttle , if it's going to break I'm breaking it right here , right now!! 10 full Dyno pulls from 3000 rpm until the rev limiter pulls the plug... Chopped throttle engine braking between runs...and then shut it off for a few minutes while the Dyno fans cool things off a bit while you check out the power curves and air /fuel ratio graphs...

Let's say this particular 450 engine is supposed to come in at 60hp... Your first set of runs may average a disappointing 54hp...

But, as ring seal increases, it ALWAYS plays out like this...

Next set of 10 runs nets you an average of 56hp..

Cool down a bit....

Next set of 10 nets you 58hp average...

Cool down...

Next set.... And from there on... You now "have an engine" perfect ring seal and 60hp from there on out .... Finish your tuning and testing... And from there on out when you test that engine after a warm up, you're pulling 60...

Consistent... Repeatable... Documented to death on Dyno run after Dyno run.... That's how it goes every time...

Hope that long term real world experience sheds some extra light...

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Side note...

Not that it has any real bearing or basis...

It's just what I prefer to do... 

The oil I use for all initial cylinder wall oiling wipe down is Klotz Super Techniplate 2 stroke oil...

Mixes and burns well/clean with gasoline in combustion chamber... Never had a single problem... So never had reason to not use it ..

And if you could pick one smell that evokes all the joyous memories of off road racing from my youth in the 70s... !! Racing Castor oil... MMMMMMmmmmmmmmm

If there is an off road heaven... That smell is it... Or I'm not interested...

 

Lol

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Hi Grayracer513,

Great article. You write very little about conventional camshaft & lifters. I mean the basic tappet style. What is your recommendation to break in those? 

My experience is that the rotating parts with hydrodynamic wedge are easier to break in, it's the parts where this won't happen that can cause trouble. Like tappet lifters, rocker arms (specially the ones with ball type adjustment), valve stems and such. I've just lightly lubricated piston ring sides and piston skirt, but rings dry. We was running a methanol dragster where the engine was apart quite "often" so we had a lot of break in preriods. 

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1 hour ago, mixxer said:

Side note...

Not that it has any real bearing or basis...

It's just what I prefer to do... 

The oil I use for all initial cylinder wall oiling wipe down is Klotz Super Techniplate 2 stroke oil...

Mixes and burns well/clean with gasoline in combustion chamber... Never had a single problem... So never had reason to not use it ..

And if you could pick one smell that evokes all the joyous memories of off road racing from my youth in the 70s... !! Racing Castor oil... MMMMMMmmmmmmmmm

If there is an off road heaven... That smell is it... Or I'm not interested...

 

Lol

Love the smell of bean oil in the morning! Lol...It's been sometime since I've smelled that aroma!

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Very enthusiastic article, with all respect a bit over the top. It is important to write about two major differences in drivin or riding on a motorcycle.

 

First use of the bike: Just be a bit careful while riding keep the throttle output low and calmly use throttle a thight enduro track is the right Enviromemt, after an hour change the oils.

First use after top end job or motor rebuild including the cam and can-rod, where you just use standard motor oil for four strikes and standard two stroke oil for two strokes for initial lube while assembling and the recommended gear box oil for assembling the gearbox and clutch.

Let the bike first run at idle for 30 seconds with some calm throttle use.

Let the engine cool down do it again for a minute.

Depending the barrel you should do it a third time when you have an iron liner rebored.

Then proceed likewise as stated for a brand new bike with a an hour rum with decent throttle.

Why it's so easy and not so complicated? Because the hole package has to be "trued" again to each counterpart from gears to shafts pistons to.cylinders and con-rods, valves and valve shafts.

This is the case with modern and with older engines and especially to any rebuild engine.

 

 

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Interesting article and for sure a subject with many different myths. In my old 2-stroke days when replacing the piston I used to do a kind of dry or super dry "dead running". Before I put the head on I would rotate the motor with my hand on the kick starter while spraying a little contact cleaner in the bore. I would do this for a few minutes then clean it off, finish the assembly and for the most part run it.

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5 hours ago, mixxer said:

After a decade of owning 2 different dynojet dynos and doing thousands of runs on hundreds of fresh built race engines , I can add in something that 99.9% of people will never experience..

Beyond just the experience of breaking in hundreds of engines...

My first readings of race engine break in were in published articles long ago... Written by Jack Roush and Smokey Yunick... And what they wrote had made sense intuitively , and were of similar mindset... I had adopted their methods so very long ago , had nothing but stellar results, and have had zero reason to doubt or change it..

The idea was to take advantage of the rougher initial microscopic peaks of the machined surfaces ... Let them wear... actually force them to wear and create a piece to piece self machining polish to final fit... All while the surfaces had the original "sharper peaks" ... Make them wear while they were effective at burnishing... Shave the peaks off under pressure as opposed to lower pressure operation that would let the peaks round off and permanently reduce their effectiveness , or chances of, ever achieving perfect break in or seal ... So the biggest concern for power production is the Holy Grail of "seeing if you have an engine at all" : the ring seal... Universally accepted by all engine builders is that ring seal is the bottom line of if you have a race engine, or if you don't.... Packing and lighting a fantastic charge of air fuel mix doesn't amount to much if you aren't sealing that pressure close to 100% and making that charge WORK for you... Plus the hot blowby past the compression ring is responsible for so many accelerated bad processes that the downsides of bad ring seal go exponentially beyond just power loss...

The methodology and reasoning for break in from both of the legendary endurance race engine builders sums up something like this...

Let the engine slowly warm up to operating temperature without much load at all.... Letting parts achieve their "at temp/ hot running shape" before going hard at break in ... Pistons for example are neither round nor cylindrical when cold, as their cold shape has to allow for the large heat gradient and differential expansion from combustion chamber heated top, to the bottom of heat shielded and heat sinking skirt...

So... Slow/ unloaded warm up to operating temperature.... Then the equivalent of full throttle acceleration through 2~3 gears at a time.... No extended high rpm running... But full throttle and shifting appropriately... Combustion pressure forcing rings and cylinder peaks to shave off before the round off and become dull ...

Then chopped throttle engine braking with the idea that the vacuum above the piston will assist in pulling a small amount of oil around the ring set before the next acceleration run... Lubrication / cooling/ debris washing...

Then hit it again for a 3 gear run.... In sequence for about 15 minutes... Roughly the equivalent of a 15 minute moto except for extended engine braking after each 3 gear blast...

After 15 minutes ,change the oil and filter... You're done!

Now... Back to dyno running...and the breaking in of hundreds of fresh top end race engines.... On the dyno...

Through the series of pulls , you would get to watch the effects of ring seal as power rose through each successive set of runs... Ring seal increases, power goes up... You can see on the graphs when you "have an engine"...

Bring it up to temp just lazily running the machine spinning the dyno drums...  Shut it off and let it heat soak... Run it spinning the drums again ... Then when it's warm....

Full throttle , if it's going to break I'm breaking it right here , right now!! 10 full Dyno pulls from 3000 rpm until the rev limiter pulls the plug... Chopped throttle engine braking between runs...and then shut it off for a few minutes while the Dyno fans cool things off a bit while you check out the power curves and air /fuel ratio graphs...

Let's say this particular 450 engine is supposed to come in at 60hp... Your first set of runs may average a disappointing 54hp...

But, as ring seal increases, it ALWAYS plays out like this...

Next set of 10 runs nets you an average of 56hp..

Cool down a bit....

Next set of 10 nets you 58hp average...

Cool down...

Next set.... And from there on... You now "have an engine" perfect ring seal and 60hp from there on out .... Finish your tuning and testing... And from there on out when you test that engine after a warm up, you're pulling 60...

Consistent... Repeatable... Documented to death on Dyno run after Dyno run.... That's how it goes every time...

Hope that long term real world experience sheds some extra light...

Well said.....

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8 hours ago, Marek0086 said:

If anything...   having oil in the ring grooves would IMPROVE the seal between piston and rings.  And also the seal between ring and bore. 

Gasses travel easily through gaps that liquids will not. To seat rings properly, they must have adequate gas pressure behind the ring to press them into the cylinder. This is how compression rings work. If you load the ring gap with motor oil, you will not get the necessary gas pressure to seat your rings properly. The author DID emphasize to use oil sparingly. I watched a new engine get ruined because the builder thought immersing the pistons in a small pail of 30wt before installing them was a good idea. Like you, at that time, I didn't know any better either.

To repeat a similar experiment without damaging an engine, fill your garden hose all the way up with sand, attach it to a faucet, turn the faucet on, and report back how much water flows out.

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Smokey Yunick...

Smokey Yunick was called 'Smokey' not because of the pipe he clenched between his teeth, but because all his engines visibly burnt oil. He was a notorious cheat and never accomplished anything except for new ways to cheat. Case in point; his 2" diameter 'fuel line' that ran back and forth under the car as many times as possible before reaching the engine compartment.

He actually drove the car from tech inspection, around the track and back to his pit with the fuel tank removed, still back in tech inspection. :lol:

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15 hours ago, grayracer513 said:

1) Heat "cycling", or heating and cooling repeatedly for its own sake doesn't really accomplish anything, as it does not change the properties of the metal parts, and it causes no wear in and of itself.  Break in is a controlled, moderated wear process.  Heating and cooling just so it can be heated again doesn't contribute anything.

2) This makes me wonder if you read the article at all, since the wear in needs of all types of the moving components were discussed at length, including ball and rolling element bearings as used in the crank assembly, and plain surfaces such as the cam shafts, lobes, and lifters. 

1) 90% of the heat adsorbed by the piston leaves through the rings. Until the rings are properly seated, you don't get that heat transfer, which is why some people recommend letting an engine cool in between 'break in sessions'. I agree with you that it has nothing to do with metallurgy.

2) Not sure whether I am agreeing or disagreeing with you, but plain bearings, cam journals and cams are broken in by temperature (not metallurgical) and hydrodynamic lubrication conditions, not by wear friction. Until they build up a film barrier, they are vulnerable to damaging friction. Any wear to a bearing, journal or cam is incidental, and not desirable, which is why a new cam is broken in by starting the motor and immediately  going to the engine speeds that promote hydrodynamic lubrication.

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The factory approach to addressing issues that turn up at this point also varies, but any bike that makes it to the dealer has been run long enough to skip the initial steps above and go right to the second phase; run it  for about the first 10-15 minutes at up to about 60-75% of its capacity, then step it up for another 10 to 15.  You want to avoid thrashing it right at first, but don’t “baby it” during the process, either.  Shut it down, look it over, and if all looks well, call it done and have at it.  

The truth is that the break in period has been reduced to a less than one hour experience by improvements in metallurgy and machining methods, improved engine oils, and proper assembly practices.

True in part, but your time period differs greatly with the instructions provided by the manufacturers, which most certainly have staff engineers that sit on the board of the SAE.

 

 

BTW, one of the better articles on proper engine break-in I have ever read. :thumbsup:

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Edited by Bermudacat

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Sorry kids...

Unless you have personally broken in hundreds of race engines on a dyno...

You really got nothing to say.... 

There is a difference between knowing...  And merely repeating stuff you have heard... Like a parrot ... A parrot can talk all day long, but it has no idea what it said...

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17 hours ago, mixxer said:

Sorry kids...

Unless you have personally broken in hundreds of race engines on a dyno...

You really got nothing to say.... 

There is a difference between knowing...  And merely repeating stuff you have heard... Like a parrot ... A parrot can talk all day long, but it has no idea what it said...

If your just some guy in a garage, good for you. If you know so much better than the engineers that build them, great, but I think I'll listen to the engineers. :D

(Good job regurgitating the Magical Moto Man Method of destroying an engine during break-in, Mr Parrot. :thumbsup:)

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On 8/7/2017 at 9:45 PM, cowpie said:

i agree to the point of not worrying too much about a new engine, but just run it on the easy side for awhile and 'do' heat cycle it .. the factor mr qualified expert misses is parts expand and contract with heat and going out and being hard on it can make things go out of tolerance to the point of damage before theyre polished in good ... coating them with 'fantasy blend' synthetic wonder oil is a mistake to, sorry, but it is  ... and the worst idea promoted, it will take 10k miles to fully break in because 'point B' mr quailified expert misses is more than the top end on a bike is breaking in .. but really, theres nothing better to me than watching some idiot haul his brand new supersport bike into the dealer with holes blown in the pistons and everything else because he went out and did a 'hard' break-in .. its a beautiful thing actually ..

It will only take 10k to break in if you do the heat cycle and baby it.

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as soon as i saw this article

i knew there would be tons of comments by people who like to talk about the magical heat cycle, but cant tell you what it accomplishes.  They want to spread it because its what they were told to do, and what they have done, and they don't want to admit that they have not done it the best way on their "bad ass" motors.

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Looking for some wisdom, have a 05 drz400sm and will be installing 434 bb stage 2 cams fcr41 and procom cdi. Would like to know recommended jetting and thoughts on gearing for street

20170817_195855.jpg

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On 8/15/2017 at 0:44 PM, EnglertRacing said:

as soon as i saw this article

i knew there would be tons of comments by people who like to talk about the magical heat cycle, but cant tell you what it accomplishes.  They want to spread it because its what they were told to do, and what they have done, and they don't want to admit that they have not done it the best way on their "bad ass" motors.

Nothing "magical" about the fact that 90% of the heat from the piston leaves via the rings, and until the rings are seated, you can cook your piston if you use the Magic Moto Maggot Method of break-in. Clearly your own myths of engine break-in are leaving you in a defensive mood. :smirk:

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