Which break-in style works best? Easy or Hard?

schaubster

Been Around the Block
I think this discussion has been had but i thought it would be interesting to get the perspective of people that have actually done it.


What type of break-in do you think works best on a rebuild. Easy break-in like the manufacturer suggests or hard break-in like professional racers do.


Thoughts?
 
I just fired my bike up for the first time last week (after my rebuild). I'm planning on a hard break-in.

Not sure how you consider a break-in to be a "success" until you pull the engine apart the next time, but I'll be sure to report if anything breaks off instead of breaks in. :p
 
There is no benefit to abusing a new engine. Modern ring profiles break in just fine with normal use. Pay attention to the manufacturer's guidelines. Don't rev hard, don't sustain high speeds, don't be heavy on the throttle except very briefly. There is no reason to scuff engine parts. Take it easy on a new engine, especially the first 50-100 miles.
 
I imagine anyone that has an opinion about this will be pretty passionate about their side. It just seems strange to me how different groups (manufacturers & professional racers) have such different methods.


From what I've heard, doing a hard break-in sets the rings better but that seems risky because if there is anything wrong it will probably happen soon after your rebuild.
 
The goals of manufacturers and of racers are different, no? It would stand to reason that the two different groups do more than just break-ins differently.
 
Race engines are also usually built with a little looser tolerances. An engine built for the long haul is built tight, and broken in gently. A tight engine run excessively hard will end up with scuffed pistons, and lose some of the long life benefits of being built to minimum tolerances.

I used to break in my race engines by running at 1/2 throttle or less for the first 30 minutes. That was it. 30 minutes break-in.
 
I fall into the "hard" camp. You gotta seat those rings while there's still a good hone on the cylinder walls. Just be sure to change the oil often during the first few hundred miles.
 
AlphaDogChoppers said:
Race engines are also usually built with a little looser tolerances.

Not so sure I can get on board with this without some corroborating evidence. Formula 1 engines won't even turn over until they've been heated up because clearances are so tight. I'm sure you've heard of blueprinting an engine; ensuring everything is tighter than factory spec?
 
Yes! Is there anyone that has broke in their engine hard with good, bad, or no different results?


I'm really curious to hear some first hand accounts.
 
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I'm actually interested in this as well, but coming from a 4-wheel mechanic background I'd like to know where the two-wheel machines coexist. I would like to give my 2 cents though. Grab a bentley or Haynes manual and read up. Not following manufacturer recommendations can lead to cam lobe scoring, piston scuff, etc.. Most manufacturers have different specifications for the level of said rebuild as well.
A long block rebuild will not go through the same break-in as, say, a top end rebuild. Never assume the recommended break-in procedures are the same for two different engines either. A lot of controls will dictate the whether premature failure on certain parts or the entire motor, for that matter, may be feasible in the near future. Such as quality of engine oil, quality of parts, controled cleanliness during assembly, lash on moving parts, and torque specs. For example, if you overtighten your main bolt torque specs, it won't matter what engine break-in you use.
My point is that following someone who "thinks" their way is a good break-in is, likely, incorrect.... And probably started doing it that way from someone else's verbal advice. Even a mechanic, who's been doing his job for 35+ years may think he's doing it the right way(because it works), but if he's not following the specs the manufacturer provides then it is likely the engine will not last as long as had been initially possible. The people who originally made your bike spent countless hours, and money, in R&D to give the best possible results. I would advise following what they provide.
 
I firmly believe in a nice easy break in period whether it is one of our stock or race engine builds and would never personally even consider or recommend breaking any engine in hard.

I also have to agree with Brother Sonreir on the clearance issue, as a general rule race engines are built with much closer tolerances than what the factory recommended clearances are. I run very close exacting tolerances in all of my race engine builds, for example we run nearly zero end gap clearance on compression rings in certain engines.

Although most all tolerances in a race engine will be closer than factory specifications there are exceptions to the rule, for example in a CB450 engine with racing profile cams we run .004" intake and .005" exhaust lash clearances which is much greater than the recommended factory clearances for that engine however we also recommend those same clearances on a stock CB450 engine over the closer tolerances that are recommended in most manuals as the CB450 is very hard on the valvetrain and running the .004" and .005" lash clearances will help extend the life of the valvetrain components in that particular engine.
 
Okay just my 2 cents, first 50 miles are the most critical, extreme heat from ring break in, vary the throttle, no more than 3000 RPM. After that run with varied throttle like you will normally ride, but no long full throttle runs for the first 200 miles, after that ride it the way you ride.....period. Change oil at 500 miles and 1000 miles, follow manufacturers recommondations from there. I have done this with all new engines for the last 35 years with no problems, whether air cooled, water cooled, race, or street, this works. Good Luck
 
BAck in the day - where have I heard that before?- Race motors were set up loose because they would seize from the extra heat causing pistons to expand more. We set up piston-bores slightly on the tight side for race motors to retain a higher compression with less leakdown.

The key to a successful break in is low stress - you and the motor. Start off with a couple of static heat cycles. Run the motor and slowly raise the revs until it's at full operating temperature - just blip the throttle lightly - no big handfuls.

Then let it cool down and a few hours later repeat that process. All you are doing is varying engine speed up to say 3 k the first time and say 50% of the redline the second time. Don't let it get too hot. It's a low load reasonable speed heat cycle.

Then let it cool again and check it from end to end. Anything come loose? Any leaks? and so on.

When you ride it you want to do the same thing. On each successive 10 mile loop, let the revs go a little higher but no hard acceleration. Once you have it up to say 80% of redline - again with low load and not a lot of throttle, bring it in and check it over again.

Next time out use slightly more throttle to apply more load. Repeat until you have it up to full revs and more or less full throttle.

As you probably worked out, revs are OK, load will potentially damage a fresh motor.

We do the same with race motors. The only difference is the number of miles and we go a lot faster on a little throttle.
 
Teaser, what you describe is very much like what S&S break-in instructions were for their engines. They insisted on a few static heat cycles and gentle, varied operation during break in. Commonly believed myth is that the rings will not seat properly unless you "run the Hell out of it" are really just often repeated Internet lore with no scientific or technical basis.

Here are the current S&S break in instructions.

Engine Break-In
During the first 500 miles of operation, critical parts are “breaking-in” against each other. For this reason:
[list type=decimal]
[*]Avoid excessive heat build-up. Do not allow engine to idle for long periods of time.
[*]Keep the outside of the engine clean.
[*]Do not subject engine to unusual stress or load as with sidecar or trailer.
[*]Avoid hard acceleration until the engine is warmed up.
[*]Do not lug the engine. Vary the engine speed; avoid maintaining a steady speed for long distances.
[/list]First 50 Miles (80 Kilometers) –
[list type=decimal]
[*]Without lugging the motor, do not exceed 50 mph (80 km/h).
[*]Keep the engine speed below 2,500 RPM.
[*]Change the oil and filter at 50 miles (80 kilometers).
[/list]Up to 500 Miles (800 Kilometers) –
[list type=decimal]
[*]Do not exceed 65 mph (105 km/h).
[*]Keep the engine speed below 3,000 RPM.
[*]Change the oil and filter at 500 miles (800 kilometers).
[/list]Up to 2,500 Miles (4000 Kilometers) –
[list type=decimal]
[*]Keep the engine speed below 3,500 RPM.
[/list]They used to have more detailed instructions with regard to static heat cycles before actually riding the bike. I thought I had it as a PDF. I think S&S now does those static heat cycles at the factory before shipping the engine.

It's a method that I fully subscribe to. Some of it is a little more conservative than is necessary for lower performance engines, but the common sense of these instructions strike me as the correct method.

My car, which I bought new 14 years ago, has 276,000 miles on it. I drove it gently for the first 1,000 miles. It never saw full throttle until 800 miles. It never burned a bit of oil and still runs like a top more than a quarter million miles later. I started using synthetic oil at 8,000 miles and used extended oil change intervals, sometimes as long as 25,000 miles between changes, and it still never needed oil added between changes until well after 200,000 miles.

A lot of break-in lore comes from the days when cylinder bores may not have been so precise and round. Rings were thick, stiff, not very round, and made of cast iron. Those rings DID take a while to seat in. Still, they would eventually seat in, no matter what break-in method was used. Continuous high speed, however, would take a toll on a new engine. Lubrication was not as good then, either.

Modern engine building has far more sophisticated ring profiles. Rings are much more flexible and the metallurgy is completely different. Cylinder hone finishes are much finer than they were in the '60's when you needed a pretty rough finish to wear in the crude cast iron rings of the time.

Sure, there are plenty of people who have "run the piss" out of a new engine, and "never had a problem. Will they get maximum service life from an engine broken in that way? Doubtful.
 
Yea, you get your brand new bike and carefully run it in - no excessive revs and more important no lugging, change the oil at 500 miles, dah, dee, dah, dee dah.........

Oh yes, the MINUTE your brand new bike [ or car ] came off the production line - it was put on a set of rollers and had the balls revved off it through the gears :eek: , peaking in each gear. Then some [ like Ducati ] would go out for a blind around the factory test route ............. then you get it and go through the running in proc .............

Provided the oil is allowed to circulate around the engine and get up to temp [ if using monograde ] - then it's ready to go - IMO. ;D
 
<<it was put on a set of rollers and had the balls revved off it through the gears
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, peaking in each gear.>>

Yeah, we've all heard that as an excuse to abuse a new engine. Those factory dyno tests are probably not even 2 minutes long. The engine does not have time to build up excessive heat. Probably doesn't even get up to full operating temperature, and the oil certainly never gets up to temperature. They only run it long enough to detect obvious engine defects.

But we are not talking about a new bike at the factory that will get a new engine if it grenades on the dyno. We are talking about a rebuild. What would be the point of abusing a new engine if you don't have to for manufacturing production purposes?
 
beachcomber said:
Yea, you get your brand new bike and carefully run it in - no excessive revs and more important no lugging, change the oil at 500 miles, dah, dee, dah, dee dah.........

Oh yes, the MINUTE your brand new bike [ or car ] came off the production line - it was put on a set of rollers and had the balls revved off it through the gears :eek: , peaking in each gear. Then some [ like Ducati ] would go out for a blind around the factory test route ............. then you get it and go through the running in proc .............

Provided the oil is allowed to circulate around the engine and get up to temp [ if using monograde ] - then it's ready to go - IMO. ;D

It's funny you should mention that. I was watching a program on the television a couple months about about how Goldwings were manufactured. They showed a guy doing just that. Right off the assembly line the Goldie was warmed up and put onto a dyno and redlined through each and every gear (even reverse, WTF?)

For those of you who have not read the following article, please do. More fuel for the fire. :D

http://www.mototuneusa.com/break_in_secrets.htm

This part I find quite funny, actually:
MotoMan said:
Yamaha's break-in recommendation for the RX1 has been to idle the engine for 15 minutes.
Some owners found that the heat build up from doing this was so extreme,
that their taillight had begun melting (!!!)

Yamaha has since changed the recommendation to three 5 minute idle periods.

Another highlight is the following pic of pistons taken from two Honda F3s. According to the article both bikes were fresh from the factory and run stock. The ONLY difference between the two was the break-in method and each bike was run over a full season of racing without engine rebuild. Factory break-in on the left with hard break-in on the right:
BreakInF3Pistons.jpg



Assuming it's true, it can be counted as anecdotal evidence that at least one manufacturer doesn't even use their own break-in methods before suggesting them to customers.
 
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