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Howdy guys, I have 2 brand new mowers coming in tomorrow or the next day and what i'm concerned about is how to do a proper engine break-in. Now this seems like a simple task because all I should do is follow the owners manual right...but the guy at the dealership says to run them full throttle. his theory is to break them in the same way you're going to run them. what do you guys think?

One of the key aspects of breaking in a new engine is to start at lower RPMs and vary the engine speed periodically during the first hour, with short periods of full throttle. Shut it down and inspect it for any sort of leak, fuel ,oil and exhaust. Make sure that the choke is opening fully when the lever is in the full open position.
Some engines may take up to 50 hours or more of normal operation before they settle in and stabilize both fuel and oil consumption. During this time, I suggest following the manufacturers oil change recommendations and check oil levels periodically. Read and understand the procedures for correctly checking the engine oil level as this varies between engine types.
I also suggest using the manufacturers engine oil and filters while the engine is on warranty.
If the engine manufacturer allows for full synthetic engine oil, don't switch to it until after 50 or more hours are on the engine and the engine fuel and oil consumption has stabilized.
Just my thoughts!
Mad Mackie in CT:laughing::biggrin::smile:

mikeb1982 said:

Howdy guys, I have 2 brand new mowers coming in tomorrow or the next day and what I'm concerned about is how to do a proper engine break-in. Now this seems like a simple task because all I should do is follow the owners manual right...but the guy at the dealership says to run them full throttle. his theory is to break them in the same way you're going to run them. what do you guys think?

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Listen to the guy at the dealership. His theory about breaking them in the same way you're going to run them is correct, WOT. New engines will take time to develop full power. Mower decks and drive systems have higher friction when there new placing additional load on the engine. It generally takes 40 to 50 hours of break in time for a new engine or machine to develop it's full power and best performance.

You need to take into account that an air cooled engine gets its cooling air from the fan under the housing. Lower rpm's can actually increase engine temperature when running under load. Go by what is in the owners manual for your engine.

Most manufacturers state that a problem will most likely occur in its 1st 5 hours due to their r & d during testing.

I would possibly change oil after 5 hours but use machine at wot.

Check and keep filter clean.

I understand the cooling aspect. I generally like to give a new engine at least an hour of no load operation, varying the RPM with several WOT periods, shut it down let it cool and inspect it before putting it into WOT operation with a load.
Bear in mind that I'm a retired piston engine experienced aircraft mechanic and was responsible and liable for the aircraft when I signed the airworthiness certificate and many times flew in aircraft that I had worked on in both military and civilian aviation worlds.
Aircraft engines, both new and overhauled are run in before delivery, small power equipment engines are usually not run in and I prefer to give them a little consideration and respect before putting them into full service, however almost impossible to do with generators!!!
I fully understand that time is money particularly to small businesses, been there, done that.
Just my way of doing things!
Mad Mackie in CT:laughing::biggrin::smile:

The guy at the dealership is right, run it like you are going to use it which will force the rings to seat. 5-8 hours, then change the oil to either typical dino oil or a group III synthetic (Rotella T6 is a group III). A group III synthetic is actually not a synthetic at all, just a highly refined mineral oil than can legally advertise as synthetic. Do not run a group IV or V synthetic like Amsoil or Royal Purple until you have at least 50 hours on the engine. Officially Kohler says to wait 50 hours, Briggs says you don't need to wait at all and can even use synthetic for break in, and Kawasaki makes no recommendation except they want you to use their KTech which is a synthetic blend in most weights.

Mad Mackie said:

I understand the cooling aspect. I generally like to give a new engine at least an hour of no load operation, varying the RPM with several WOT periods, shut it down let it cool and inspect it before putting it into WOT operation with a load.
Bear in mind that I'm a retired piston engine experienced aircraft mechanic and was responsible and liable for the aircraft when I signed the airworthiness certificate and many times flew in aircraft that I had worked on in both military and civilian aviation worlds.
Aircraft engines, both new and overhauled are run in before delivery, small power equipment engines are usually not run in and I prefer to give them a little consideration and respect before putting them into full service, however almost impossible to do with generators!!!
I fully understand that time is money particularly to small businesses, been there, done that.
Just my way of doing things!
Mad Mackie in CT:laughing::biggrin::smile:

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Wors't thing you can do to a new engine is to idle it
Second worst thing is to have it run no load for extended periods.
Rings need back pressure to get them to seal properly to bores, oil seals need pressure to seal the lip against the shaft.


So it is WFO, the regulator will determine how far to open the throttle.
When you are mowing, go slow fast slow fast to apply varying load on the engine as the govenor will determine the actual throttle opening.
Start with light cuts and bring them up to full working cuts over time.
If you can do it also run a lite cut for the first hour or so, occasionally dropping the deck to full cut to again vary the load, you want the engine to work a bit but not to labour so it should bog for a tiny second then catch up to full speed quickly.

Here is the difference between people that work on $1,000 engines verse people that work on $100,000 engines!

Mad Mackie said:

Here is the difference between people that work on $1,000 engines verse people that work on $100,000 engines!

Click to expand...

And things that work on aero engines or race car engines do not necessarily apply to mower engines

In this thread knowledgeable people have responded. Years ago I read wide eyed the report from inside Porsche where the newly built AC engines were started, warmed up and pegged @ 7000 rpm. That after very old wives' and folk wisdom suggesting various remedies. Like sprinkling Bon Ami in each cylinder to seat the rings, ouch. Assuming round bores, proper rings, etc I guess such initial loading will not hurt, in fact help........if you have Porsche precision. Perhaps the middle ground and making sure there is adequate oil. Oh... and my favorite. Why don't mfgrs install an oil pressure gauge on every dash of every AC powered rig? Even if only some glanced now and then at the readings many failures could be avoided. Or at least BIG,RED idiot lights? (Perhaps some do).

I am not sure a big red idiot light would do it in some cases. More like a big hammer to hit them on the head to get their attention. And even then some wouldn't know what just happened.

I bought some 2 1/2 " dia key rings and had some promotional key tags made.
I hang these around the dip stick on mowers when I return them & suggest that for safety reasons ( kids can't accidentally start the mower ) the owners should leave them there.
Logic behind this is if you take the keys from around the dip stick there is a better than average chance you will check the oil before you start the mower.

Best one was a customer who say a big oil puddle under the mower so they started it to move it out of the way to see where the oil was coming from.
Exit piston crankcase left.

For many years I used to flood rings with oil when reringing engines however some long conversation with John Heaney ( Triumph race tuner ) soon had ne doing dry ring installs. no idle after first start and on the road strait away, adjust the carboy when you get back.
Rings generally bed in strait away and have never had a failure since.

Ya'll settle down now, before I report ya's to the ...... NO testosterone or Viagra List-keeper !! :laughing: :laughing: :laughing: :biggrin:

A lawn mower cuts grass wide open. An air cooled engine cools wide open. Very seldom and momentarily at that do we run them any other way. Changing the oil and filter at the first interval mentioned in the book in my opinion is he most critical thing one can do for a new engine.

I never had valve or ring issues in any of my engines by following this method. I'm 53 so I've been running engines for a few years now.

Snow blowers, lawn mowers, tillers, tractors and my cars are all done the same way. I don't follow a special break in procedure on anything I own. When the machine is brand new, I respect the machine a bit so I run them 80% throttle for the first hour or so. Just take it easy.

A slight warm up is done always when they are first fired up to get the oil flowing. Don't beat them to death when you first run them if they are not up to full temperature. Listen to the motor, if it's laboring some, back it off a little.

Most importantly, change the oil and filter when you should.

B&S says don't put engine under full load for 50 hours..
There is also "Break In Oil"
I'm trying it in my new engine..
High Zinc Engine Break-In Oil