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Old 03-25-2010, 05:54 AM   #1 (permalink)
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Engine rebuild break in

Just wondering what everybody's opinion is on breaking in a Harley Davidson V-twin engine. I'm finishing up an overhaul on my 2007 1200 sportster. I upgraded the cams, pistons, pushrods, heads, etc. I did not bore it or increase cc's. I know that Harley recomends that you break in a brand new stock harley "gently" for the first 500 miles. I did this when the bike was new. My question is should I break her in easy after a high performance rebuild, or should I break her in hard? Thanks for the help.
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Old 03-25-2010, 06:00 AM   #2 (permalink)
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500 miles will do it, but I go 1K, better to be safe than sorry!
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Old 03-25-2010, 06:08 AM   #3 (permalink)
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I'd still run it "conservatively" for the first 500 miles, as other parts are new, other then the bore. Cams, etc. Change the oil and filter, check for odd debris, then ride it how you want....
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Old 03-29-2010, 08:33 PM   #4 (permalink)
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Quoted from Axtell

“Breaking in your motor is vital to the life of your engine. Axtell’s recommended method of break-in is to heat cycle the motor. Start the motor (with plenty of air blowing over the motor to dissipate heat) and allow it to run for thirty seconds. Allow the motor to completely cool to room temperature.
Once cooled, start the motor again and allow it to run for sixty seconds followed by a complete cool down. Repeat this process, adding thirty seconds each time until you have reached four minutes.

Now the vital break-in is done. However, over the course of the next thousand miles, the internal components are still familiarizing themselves with one another, so take special care during that time.

Keep your engine under 3500 RPM’s for the first 300 miles, and less than 4000 RPM’s for the first 1000 miles. Do not put a large load on the engine and be careful not to “lug” the engine during the 1000-mile break in period.”
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Old 03-29-2010, 10:25 PM   #5 (permalink)
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What they said!
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Old 04-06-2010, 07:27 PM   #6 (permalink)
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motoman method



The results are always the same... a dramatic increase in power at all RPMs. In addition, many professional mechanics have disassembled engines that have used this method, to find that the condition of the engine is much better than when the owner's manual break-in method has been used.

The thing that makes this page so controversial is that there have been many other break-in articles
written in the past which will contradict what has been written here.

Several factors make the older information on break-in obsolete.

The biggest factor is that engine manufacturers now use a much finer honing pattern in the cylinders than they once did. This in turn changes the break-in requirements, because as you're about to learn, the window of opportunity for achieving an exceptional ring seal is much smaller with
newer engines than it was with the older "rough honed" engines.

In addition, there is a lot less heat build up in the cylinders from ring friction
due to the finer honing pattern used in modern engines.

The other factors that have changed are the vastly improved metal casting and machining
technologies which are now used. This means that the "wearing in" of the new parts
involves significantly less friction and actual wear than it did in the distant past.


With that in mind ...

Welcome to one of the most controversial motorsports pages on the internet !!



How To Break In Your Engine For
More Power & Less Wear !

One of the most critical parts of the engine building process is the break in !!
No matter how well an engine is assembled, it's final power output is all up to you !!

Although the examples shown here are motorcycle engines,
these principles apply to all 4 stroke engines:




What's The Best Way To Break-In A New Engine ??
The Short Answer: Run it Hard !

Why ??
Nowadays, the piston ring seal is really what the break in process is all about. Contrary to popular belief, piston rings don't seal the combustion pressure by spring tension. Ring tension is necessary only to "scrape" the oil to prevent it from entering the combustion chamber.

If you think about it, the ring exerts maybe 5-10 lbs of spring tension against the cylinder wall ...
How can such a small amount of spring tension seal against thousands of
PSI (Pounds Per Square Inch) of combustion pressure ??
Of course it can't.

How Do Rings Seal Against Tremendous Combustion Pressure ??

From the actual gas pressure itself !! It passes over the top of the ring, and gets behind it to force it outward against the cylinder wall. The problem is that new rings are far from perfect and they must be worn in quite a bit in order to completely seal all the way around the bore. If the gas pressure is strong enough during the engine's first miles of operation (open that throttle !!!), then the entire ring will wear into
the cylinder surface, to seal the combustion pressure as well as possible.


The Problem With "Easy Break In" ...
The honed crosshatch pattern in the cylinder bore acts like a file to allow the rings to wear. The rings quickly wear down the "peaks" of this roughness, regardless of how hard the engine is run.

There's a very small window of opportunity to get the rings to seal really well ... the first 20 miles !!

If the rings aren't forced against the walls soon enough, they'll use up the roughness before they fully seat. Once that happens there is no solution but to re hone the cylinders, install new rings and start over again.

Fortunately, most new sportbike owners can't resist the urge to "open it up" once or twice,
which is why more engines don't have this problem !!

An additional factor that you may not have realized, is that the person at the dealership who set up your bike probably blasted your brand new bike pretty hard on the "test run". So, without realizing it, that adrenaline crazed set - up mechanic actually did you a huge favor !!

--------------------------------------------------------------------------------



On a Dyno:
Warm the engine up
completely !!

Then, using 4th gear:

Do Three 1/2 Throttle dyno runs from
40% - 60% of your engine's max rpm
Let it Cool Down For About 15 Minutes

Do Three 3/4 Throttle dyno runs from
40% - 80% of your engine's max rpm
Let it Cool Down For About 15 Minutes

Do Three Full Throttle dyno runs from
30% - 100% of your engine's max rpm
Let it Cool Down For About 15 Minutes
Go For It !!
Frequently asked Question:

What's a dyno ??

A dyno is a machine in which the bike is strapped on and power is measured.

It can also be used to break in an engine.


NOTE: If you use a dyno with a brake, it's critical during break - in that you allow the engine to decelerate fully on it's own. (Don't use the dyno brake.) The engine vacuum created during closed throttle deceleration sucks the excess oil and metal off the cylinder walls.

The point of this is to remove the very small (micro) particles of ring and cylinder material which are part of the normal wear during this process. During deceleration, the particles suspended in the oil blow out the exhaust, rather than accumulating in the ring grooves between
the piston and rings. This keeps the rings from wearing too much.

You'll notice that at first the engine "smokes" on decel, this is normal, as the rings haven't sealed yet. When you're doing it right, you'll notice that the smoke goes away after about 7-8 runs.

Important Note:
Many readers have e-mailed to ask about the cool down, and if it
means "heat cycling" the engine.

No, the above "cool down" instructions only apply if you are using a dyno machine to break in your engine. The reason for cool down on a dyno has nothing to do with
"Heat Cycles" !!!

Cool Down on a dyno is important since the cooling fans used at most dyno facilities are too small to equal the amount of air coming into the radiator at actual riding speeds. On a dyno, the water temperature will become high enough to cause it to boil out of the radiator after
about 4 dyno runs. This will happen to a brand new engine just as it will
happen to a very old engine.

(Always allow the engine to cool down after 3 runs whenever you use a dyno.)

If you're breaking your engine in on the street or racetrack, the high speed incoming air will keep the engine temperature in the normal range.
(In other words, you don't have to stop by the side of the road to let your bike cool down.)

What about "heat cycling" the engine ??
There is no need to "heat cycle" a new engine. The term "heat cycle" comes from the idea that the new engine components are being "heat treated" as the engine is run. Heat treating the metal parts is a very different process, and it's already done at the factory before the engines are assembled. The temperatures required for heat treating are much higher than an engine will ever reach during operation.

The idea of breaking the engine in using "heat cycles" is a myth that came from the misunderstanding of the concept of "heat treating".




On the Street:
Warm the engine up completely:
Because of the wind resistance, you don't need to use higher gears like you would on a dyno machine. The main thing is to load the engine by opening the throttle hard in 2nd, 3rd and 4th gear.

Realistically, you won't be able to do full throttle runs even in 2nd gear on most bikes without exceeding 65 mph / 104 kph. The best method is to alternate between short bursts of hard acceleration and deceleration. You don't have to go over 65 mph / 104 kph to properly load the rings. Also, make sure that you're not being followed by another bike or car when you decelerate, most drivers won't expect that you'll suddenly slow down, and we don't want
anyone to get hit from behind !!

The biggest problem with breaking your engine in on the street (besides police) is if you ride the bike on the freeway (too little throttle = not enough pressure on the rings) or if you get stuck in slow city traffic. For the first 200 miles or so, get out into the country where you can vary the speed more
and run it through the gears !


--------------------------------------------------------------------------------

Yeah - But ...
the owner's manual says to break it in easy ...

Notice that this technique isn't "beating" on the engine, but rather taking a purposeful, methodical approach to sealing the rings. The logic to this method is sound. However, some will have a hard time with this approach, since it seems to "go against the grain".

The argument for an easy break-in is usually: "that's what the manual says" ....

Or more specifically: "there are tight parts in the engine and you might do damage or even seize it if you run it hard."

Consider this:
Due to the vastly improved metal casting and machining technologies which are now used, tight parts in new engines are not normal. A manufacturing mistake causing a tight clearance is an extremely rare occurrence these days. But, if there is something wrong with the engine clearances from the factory, no amount of gentle running will fix the problem.



Q: What is the most common cause of engine problems ???
A: Failure to:
Warm the engine up completely before running it hard !!!

Q: What is the second most common cause of engine problems ???
A: An easy break in !!!

Because, when the rings don't seal well, the blow-by gasses contaminate the oil with acids and other harmful combustion by-products !!

Ironically, an "easy break in" is not at all what it seems. By trying to "protect" the engine, the exact opposite happens, as leaky rings continue to contaminate your engine oil for the rest of the life of your engine !!


--------------------------------------------------------------------------------
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Old 04-06-2010, 07:48 PM   #7 (permalink)
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Quote:
Originally Posted by GMRPERFORMANCE View Post
motoman method

............... What's The Best Way To Break-In A New Engine ??....The Short Answer: Run it Hard !..............
I know there are many ways to break-in a engine and everyone has their method but this one isn't for me. I will stick to my method and take it easy like the manual states. Has worked great for everyone of my bikes.
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Old 04-06-2010, 07:57 PM   #8 (permalink)
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Gezz Steve you like to type, We do our engine break in the same way you do (motoman)but without the dyno , our shop is right next to the freeway and the on ramp is a straight 1/8th mile shot (if a bike will run 100 mph by the end of the ramp it's a real quick one). Our philosophy has always been break it in like your going to ride it.
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Old 04-06-2010, 08:29 PM   #9 (permalink)
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Quote:
Originally Posted by tibadoe View Post
I know there are many ways to break-in a engine and everyone has their method but this one isn't for me. I will stick to my method and take it easy like the manual states. Has worked great for everyone of my bikes.
I agree that this may not be for everyone but here is one thing to think about. When I worked at a dealership way back when. I can tell you flat out that the guys doing the PDI on the new bikes where not ridding them easy. They took them out and beat the crap out of them. So maybe the large percent of new bikes already had a moto man break in on them. These guys are paid on flat rate so the faster they get one done and on to the next the more they make. Hence a WFO run up and down the freeway to get the 8-10 miles that is stated for the PDI. In the shortest amount of time makes sense to them. I amnot saying that is the way with all dealers but more than you would think.
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Old 04-06-2010, 08:38 PM   #10 (permalink)
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Quote:
Originally Posted by DBChoppers View Post
Gezz Steve you like to type, We do our engine break in the same way you do (motoman)but without the dyno , our shop is right next to the freeway and the on ramp is a straight 1/8th mile shot (if a bike will run 100 mph by the end of the ramp it's a real quick one). Our philosophy has always been break it in like your going to ride it.
YEP!
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