I've had many ABC/N engines and broke-in many, too. I've seen new out of the box ABC/N 'fits' vary somewhat...even in the same size/brand. Some new ABC/N engines are fairly loose when new...I've seen others that are tight as #ell. I'm thinking the way the late George Aldrich taught me...an ABC/N engine needs to be ran just richer than full lean for the first two minutes. I'm thinking he knew what he was talking about since he was one of few people to re-chrome cylinders and re-fit pistons to them. EVERY ABC/N engine I have ever ran that way from new has lasted a LONG time. I never have second-guessed his opinion by doing otherwise...I guess 'downunder' is going to see what could, or will, happen by running this type of engine as it is 'not supposed to be ran'. The results should prove interesting.

downunder'S ENGINE looks, smells, and even talks like a 2 stroke so I am missing your point.

I would interpret it as you completely missing the point and just picking out one little piece of information that you THINK makes your point. Did you ignore their definition of sloppy rich, and their warning to "NEVER RUN AN ABC ENGINE AT THIS SETTING" sloppy rich or at what they call "rich mixture"? And in fact, it seems YOU are the one who failed to read far enough. Instead of stopping at the definitions, you should have read far enough to get to the actual DIRECTIONS!

"1> BREAK-IN running should be done with the recommended propeller at a slightly rich setting. You want the engine to be at running operating temperatures. The needle valve should be set at a point just into this range from a four cycle setting."

Note the emphasis on SLIGHTLY, it's theirs, not mine. Slightly rich Dave. Not four cycling, not rich, not sloppy rich. Slightly rich.

You made a statement "Not one manufacturer has said that running an engine sloppy rich will hurt it....ever". I've provided several examples contrary to your statement. This discussion is over.

Edit: I didn't mean to imply the thread is over, just Dave's assertion that manufacturers have not warned users about running ABC engines too rich.

You are correct chuck....I misspoke in this sentence....

"Not one manufacturer has said that running an engine sloppy rich will hurt it....ever".

I meant to say "four stroking"....that is the topic of this debate. The person at
Mecoa that made the blanket statement about "ABC engines being damaged by
running them rich"....was incorrect. Perhaps some of the super tight K&B's could
be scuffed....

....but I doubt it.....show me one.

Our friend down-under is about to dis-spell that blanket statement....I already know
it to be false for a fact....when I broke in my first ABC engine, a S.T. .46 in 1977.
I four-stroked the snot out of it, and it was still running perfectly when I sold it
last year to a friend.....and I mean perfectly, or I would not have sold it to him....

...over 25 years later.

Rev on, my Brother.

FBD.

I have proved the point to myself on how to break in an ABC type taper bore engine. I bought two OS 32SX engines brand new and mounted them to two run stands with 100% identical set ups. I even took them apart to insure there was no remaining machining dust in them. I went so far as to torque all the screws on the engines.
Engine #1 was broken in and run slobbery rich in a cold 4-cycle mode
Engine #2 was broken in slightly rich from lean

Identical amounts of time (not fuel, since engine #1 was consuming it at a greater rate per minute than engine #2), I put a total of 20 minutes of run time on each engine in 2 minute intervals with complete cool downs between runs.

After the 20 minutes of running in, I started leaning into them and would take readings at the absolute maximum rpm. The engine broken in with a 4 cycle richness, was roughly 500 rpms weaker than the second engine. engine #1 also seemed to have a bit loser feel to it although I did'nt measure where the pinch began relative to the other engine, but it was loser

Is 500 rpms a lot, in my opinion it is, especially when I intended to use the engines on a twin. I installed the engines on a couple sport airplanes and tried to fly both of them similar amounts. What I noticed was that after about maybe two or three gallons of flying time through the previous test engines, engine #1 was significantly weaker than engine #2.

These are just my experiences a few years ago. I have been a student of the George Aldrich and Dave Geirke break-in methods for taper bore engines, so don't flame me- I believe they were 100% correct.

I'm a big fan of that show on Discovery Channel "Mythbuster". More power to you Downunder. Bust this myth about not able to break in an ABC engine slobbery rich. Of course I have no scientific info to back this up, just my big, large, overbearing support of people who can disprove naysayers. If your engine does break because of this experiment, please let us know soon so I can jump camp and say "I told you so".

Either way, looking forward to the results. Now quit bickering and just enjoy the show.

Fly NB

Dave, obviously you think you know more about this subject than the manufacturers and engine experts. I broke in my first ABC engine about the same time you did. I still have it and it still runs like new. I followed the engine manufacturer's directions (K&B), and I will continue to do so until the people who make these things, or the ones in the industry who know engines, say otherwise. Those reading this thread will make their own choice.

By golly, what have I done???


It is a good thing night comes to Israel 7-10 hours earlier than to the USA...
The responses have plenty of time to accumulate, so all can be read in one morning view of this thread...

I think Fuelman's post is the most definitive, although it also relies on only one experiment.

I think this quote;

__________________________________________________ ________________

From the Text:

FOUR CYCLING or SLIGHTLY RICH running is a rich type setting, but it is fast
enough to pull the airplane. This is the setting you normally look for before
launching the airplane because the engine will run leaner when airborne.
__________________________________________________ _________

is obviously a misprint, or an oxymoron...
When the mixture is set so rich as to cause the engine to fire on alternate revolutions, it is SLOPPY RICH and is definitely not as described... I believe Randy should proof-read this and correct it.

You'll be the first to know
OK, two more tanks today for a total of a bit over 12 minutes so now it's had 30 minutes all up. The piston still binds at the same spot and there's no change in tip movement on the prop as my rod wear indicator. The only change I've seen is a tiny polish mark about 1/16" down from the top of the piston and less than 1/8" across. Even then I only noticed it at the last minute when I held it at a different angle and the light reflected off it.

But now I'm starting to wonder just how long I should run it like this and what to do with it next. I'm of a mind to treat it more or less like a ringed engine and slowly start leaning it out, at least to the break into a 2 stroke (which I accidentally did today when I forgot to put the pressure line back on the muffler...DUH!). I'll give it at least another two tanks (12 minutes) because I want to watch that polish mark. Right now I'm just about satisfied that the rod isn't going to snap and that the piston isn't going to tear itself to pieces but I'd welcome any constructive comments on anything else to look for or maybe how much longer to continue trying to destroy it

BTW, if anyone would like to donate a Jett or Nelson I'll happily carry out the same test on them

If you try to run a Jett or a Nelson at an extremely rich setting when new (as rich as you have been doing on that no-name engine), it will come to a squeeking halt... the piston will be jammed at about top dead center, and you will have to apply some serious force to the prop to get it out of there... and it will squeek again while you are doing so...
This is caused by two factors: 1) the excess fuel washes the oil film from between the piston and sleeve, and 2) the engine will be tighter than when run up to temperature.
Also remember that when you are trying to move the jammed piston, the oil film gets pressed out from between the crankpin and conrod bearing...

So you can't do the same test on them...

Now I'm not saying this will automatically damage a rod or something, but seeing an engine coming to such an abrupt stop does not seem right to me. The forces on the moving parts must be extreme... as there is quite a bit of energy stored in a fast rotating crank and prop. If you don't believe me, put your hand into the prop of a running engine...

Jett and Nelson racing engines are so tight when new you can hardly prime them by hand... they will most likely get stuck, unless you have a very strong, fast "flick" in your wrist.
Half of the time you even have to run up your electric starter before you hit the engine with it, to prevent a sticking piston.

This description is exactly what has been happening with the K&B 3.5 that I've been breaking in. I just bought a backup that's also never been run and although I won't actually try to turn it over until I'm ready to run it, it appears it will be the same.

I should have mentioned my car engine experiments, but I was in a forum of airplane guys so I did not.
With the tight little, high reving car and buggy engines, my opinion is that running 4-stroking rich is detremental beyond a shadow of a doubt. Not too often will one spit a rod, but the difference in how long the "design fit" or pinch lasts is extremely dramatic.
Even 4-stroking rich on some of the very high performance car engines will get to the high 20K's in rpm's, with full peak performance in the high 30K's to low 40K's. I think that the high reving nature of these accelerates the pinch wearing away quicker than an airplane engine, the rod also likes to egg shape the crank pin journal when the engine is run for too long 4-stroking. Now lets aggrevate the situation by using low oil car fuel (typically 10% to 14% oil). It is quite comnmon for a car engine to only last 2 to 4 gallons of fuel when broken in to the "common, accepted" method of ideling slobbering rich for several tanks where it is so cold you can hang on to the head with your hand for the whole run.
When this is done, you notice the pinch is dramatically less than when you started.
With the car engines, I have demonstrated this to a "car engine tuning / break-in class" I hold a couple times a year at near by shops, by breaking in two OPS 12's (not cheap engines) at the same time. One I fire up for the first time and run the snot out of it in a rich but very clean 2-stroke, the other one sits and idles slobbering rich while I'm running around the other car. Its funny, the crowd thinks I'm going to completly destroy the one I'm running hard, inside a couple tanks and the one sitting ideling like the instructions state; they think will be the best.
After about three tanks ideling and three tanks on the other one running around and slightly leaning each run, we did a pinch check. Guess what?- the one that sat ideling the pinch was nearly gone, the one run around it was nice and tight. This is why car engines are only warrantied for 30 days, not 2 or 3 years or even 5 years like one plane engine manufacturer.
Guys that break in a car engine the ABC way, usually are in disbelief untill they realize that their engine is lasting 10 gallons of fuel instead of 2,3 or 4 gallons between rebuilds.

I once talked to the exclusive US importer of a very high quality, high performance (exceptionally expensive) car engine line from Europe, asking the owner why he recommended such an excessivly rich break-in, telling him that the stated method will prematurely wear the engines out. He told me laughing "Thats why these engines carry no warranty, for every engine I sell, I will sell two piston / sleeve/ rod sets" and further went on to say "the car crowd has been conditioned to wear these things out so the parts business is real good,....If we told them how to break-in and run these things right, I'd be losing a lot of money"

lets keep the flames to a minimum folks.

Has no one noticed the fuel "downunder" is using? 24% oil , 1/3 castor. Thats a lot of oil which could really skew the results of his experiment. A lot of what manufactuters tell the consumer is aimed directly at the guy who is using fuel with all synthetic oil, without castor. This done to protect themselves. I think with enough time the engine will be junk, but the large oil content will make it take much longer.
I think I use a lot of oil, at 18-20% castor blend, as compared to most flyers. I use the G/A break-in as well. Makes for some powerful long lasting motors.

It has nothing to do with Rich or Lean. It has everything to do with operating temperature. The running fits of ABC engines are designed to be correct at operating temperature, not when the engine is cool.

The engine can be run as rich as one likes provided it is bought up to operating temperature and rpm. I break in my racing engines rich but at 24,000 rpm. That rpm is the end use rpm and it will come up to temperature. I use a break in prop that has been cut down to give me the rpm and temperature at a rich setting.

Anybody who claims this is all "Hogwash" has obviously never operated high performance engines. As has been said the average ABC/AAC sport engine does not have the tighter fit of all out racing engines and will be a bit more forgiving during the early runs. However if the same principles of care and attention to detail that are applied to high performance engines are applied to sport engines it will not be detrimental to the engine or "Hogwash".

Ed S

Ed Smith,
You are absoutly correct, the issue is temp, not richness, Bravo!

In general, the richer they are, the cooler they run. Obviously this can be changed with prop load, blocking off cooling etc... The average sport modeler that breaks in his ABC type engine in a slobbery rich method with the same prop he'll fly with is more than likely going to be running it way to cold for the design fit to be achieved. In this manner, too rich equals too cold and too slow.

For what its worth, from some of my own personal experience (hands on, not 2nd hand) you can indeed wear out prematurely an ABC type engine by breaking it in running too cool (whether it be too rich, too cold outside, at a reduced throttle for too long, etc).

Some engines may be more prone than others - but I would never recommend running a lapped aluminum piston engine "slobbering rich" or at a reduced throttle setting (equally as harmfull) when new, for extended periods of time.


AJC

Fuelman, a test on only two engines is nearly meaninless. There can be enough tolerance differences between the two to account for any differences. To be a valid test, you would have to run identical tests using at least 10 engines, preferably a 100, under each condition and then noted any differences or trends. While your test are interesting, they prove nothing unfortunately.

Rodney:

You need to go back and study Fuelman's post. He did not use "Just" two engines, but rather two engines side by side in several sessions.

He didn't specify, but he may well have done this more than a dozen times, meaning at least twenty-four engines. Still not 100 examples, but more than doubling your ten engine minimum.

Bill.

Yes, and it's much more meaningful than the 1 test that the OP is doing, and some are looking at as the silver bullet that will shatter the myth of ABC breakin.

[A lot of what manufactuters tell the consumer is aimed directly at the guy who is using fuel with all synthetic oil, without castor. ]

Yes. We also need to recognize that the manufacturer must aim his directions at the "lowest common denominator" as opposed to the individual with a great deal of expertise who is able to recognize tie idiosyncrasies of the individual engine he is using. Like it or not even with the advanced technologies at industries disposal today no two engines will have exactly the same fit, etc. Unfortunately a side effect is that all but the most specialized products must have "user friendliness" rather than ultimate performance as their ultimate objective.

jess

If you already understand this, please do not misunderstand my comment as an insult- many do not know that a two stroke engine will four stroke if run rich enough. Control-line precision aerobatic engines are routinely run in a four stroke, breaking into two stroke under load as when entering a maneuver. This, of course is beside the point of the experiment under discussion.

jess

I'm not insulted at all. Especially after reading some of the stuff in this thread


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If I can show these pics I guess I'm on top of something.

Rodney,
Those were just a couple of the experiments, tests, whatever you want to call them. The single common thread to all the ABC type 2-stroke running and breaking in I've done is that hot is good, cold is not.
For example, with the OS 32SX that was run slobbery rich for break in, (and had about 500 rpm less than the other engine broken in at the same time by the correct method) all was good when I replaced the piston and sleeve much later on and the performance was right with the other one after I broke it in correctly. So tolerances and everything else aside, that is what i experienced. Even the tolerances are so good now days with CNC, I feel that is a minimum influence. I run these little model engines for a living (mostly fuel testing and comparison) but sometimes I do have the luxery of playing like I did with the OS 32's and when I teach break in techniques to car guys.

Fuelman, the downside is how many engines have been ruined because the guy gets his new GotAHaveIt ready to run souped up RC car and tries to lean it out and drag race his buddy down the street on the first tank. For him, a couple of tanks slobbering rich, even if it stays a little cool might be the right thing to do. That said, I totally agree that its a heat thing and that you must have heat in the engine to break it in correctly, just not scorching hot.

Ed M.

II think running two engines side by side is not meaningless, but not of much value either. Unless the clearances were checked before and after running. There are many fits, tapers, and tolerances manufactures can chose from and an engine made with little taper and a looser fit or harder materials may show little or no difference. I know that the LA engines are good runners while running at a full four stroke. If you follow the manual verbatim you will most likely be breaking the LA in at a full four stroke, and they seem to do well that way. On the other had if you break in a K&B 48 you will have to heat the cylinder up just to flip the prop. Four stroke that one during break in and I could see breaking the rod during a cool day. Like after an icy gust of wind. I am sure the possibilities run the gamete so I recommend following the manufactures instructions.