From: dab@vuse.vanderbilt.edu (The Nashville Flash)
Subject: Re: Breaking in an Engine
Originator: dab@space3
Organization: Vanderbilt University School of Engineering, Nashville, TN, USA
Date: Thu, 16 Apr 1992 13:40:35 GMT

In article <1992Apr16.050048.26170@seas.gwu.edu> declan@seas.gwu.edu (Declan McCullagh) writes:
>
>I got my CBR600F2 on Monday, and have since put 186 miles on it.  I've
>been wondering exactly what occurs during the initial engine break-in
>period and have heard various different explanations from various
>sources - so I've decided to appeal to the collective r.m net.wisdom.
>My admittedly unlearned understanding is that the engine parts need to
>wear in and become saturated with oil during the first 1,000 or so
>miles.  But why the magic numbers of 600 and 1,500 miles?  Just good
>rule-of-thumb intervals?
>The owner's manual says:
>	Maximum continuous engine speed during the first 600 miles
>	must not exceed 5,000 RPM.
>Wouldn't it make sense for the maximum continuous RPMs to be somewhere
>in the neighborhood of 3K RPM for the first hundred miles, than 4K for
>the next 150 miles, than 5K for the next 200 miles and so on?
>Granted, that might stifle your riding style, but for the gentlest
>possible break-in, would that not be the best approach?

Upfront Disclaimer:  I ain't no M.E.  But I have been inside a bunch of 
infernal combustion engines. :-)

When parts are fabricated, no matter how well they are polished, there remain 
marks from the machine tools used to make them.  Sometimes these are micro-
grooves, as in the case of a crank journal or cam lobe.  Sometimes they are 
visible to the naked eye, as in cylinder bores.  When the engine is 
assembled, an assembly lubricant is used in critical places such as most 
plain bearings.  Sometimes the oil pump is stuffed with grease to prime it.  
And so on.

The first time the engine is run, all of the parts get hit by oil and are
immediately "saturated."  However, that thin film of oil is pierced by the
machine marks (micro-mountains).  As the parts rub together, these peaks are 
quickly worn down.  All of the material removed by this process goes into 
your oil supply.  The worst of this is finished by about 600 miles (1000km).  
That has been discovered imperically over the last 100 years or so of data
collection by an assortment of sources.  If you care for your machine well 
over its' life, that first oil change at the 600 mile point will be the 
dirtiest oil ever to come out of your engine.  However, it may not LOOK the
worst without the aid of a microscope.

The rest of the break-in procedure is to make your rings seat.  If you run
the unseated rings at high rpm they will be unable to contain the power and
a portion of the combustion chamber charge will blow by them.  This can
cause them to never seat.  Running at an extremely low rpm does not get them
hot enough to seat them, either.  So the idea is to run them to an artifical
redline to prevent initial blow-by but still get them to start to seat.  You 
want to run up and down the gears while doing this rather than sit on the 
slab at X mph = Y rpm because running thru the gears gives the rings a 
chance to thermal cycle repeatedly.  It also helps break in your transmixer.
When the engine is run to a higher rpm the piston will go further at the
extremes of its excursions.  By 1500 (some say 3000) miles, your initial 
ring seal is established.  So having had a 5k rpm limit, you want to take it 
up higher and higher a bit at a time so that the ring/bore seal is a good 
one at TDC at high rpm.  Maybe go to a 6000rpm limit for the next 50 miles,
7000rpm/50miles, etc. until you get to the REAL redline.  Then you are done.
Remember, you only get one chance to break in a fresh engine.  How the thing 
behaves from the completion of break-in until the next rebuild is largely a 
function of that break-in.

An alternative technique pioneered by Udo Geitl (sp?) for seating rings
quickly that I have seen work is this: wash the bores with solvent and then 
soap and water, rinse well, leave out overnight.  Assemble motor with 
assembly lube on crank and cams and so on but DO NOT LUBE BORES.  Instead, 
put a thumbprint of oil on each slipper skirt of the pistons.  When ready to 
start (oil in crankcase, all systems checked), fire it up and run it to 
about 3000 rpm and hold it there for a full minute.  It will sound very 
strange "zzzzzZZZZZZZZZZzzzzrrrrr" and be difficult to attain that rpm for a 
while.  When you have run it 3000 rpm for a minute, shut it off.  Wait for 
it to cool.  Recheck head torque and ride it.  No shit!  What Udo did was 
run his pistons/bores on a spare bottom end with NO OIL for a minute to seat 
the rings.  Who is Udo?  He was Reg Pridmore's tuner back in the seventies 
when Reg won the superbike championship on a BMW.

Addendum: I once had a Chevy Citation as a company car which I picked up
new at the dealer.  I asked about break-in.  He said, "BREAK-IN?  Just drive
it like your gonna drive it."  Leased car, dealer advice, other people's
money.  OK!  So I left the dealer and drove it 80mph for 60 miles which was
my first service-call of the day.  The thing was a piece of shit the whole
time I had it.  After I left the company, a friend there told me that it
needed a new motor at 45,000 miles.  Gee, I wonder why the dealer told me 
not to worry about break-in. :-)
============================================================================
 "No hour of life is lost that is spent in the saddle." - Winston Churchill
    The Nashville Flash	  -   dab@vuse.vanderbilt.edu   -   DoD # 412 

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