I haven’t broke an engine in since the late 70’s . We would run them sloppy rich for many tanks before starting to lean them out .
I know these La engines get broke in totally different . I have the correct fuel in 5%n & 10%n with synthetic and castor oils at 11.5% each .
Can someone explained the proper break in procedures so I don’t ruin an engine !

   It's far less demanding than before, and very difficult to damage it breaking it in "wrong". Not that I necessarily recommend this, but the last one, I took it out of the box, bolted it to the airplane exactly as it came, started it, and immediately cranked it up to 14,300 RPM, fast as it will go. I have also taken them out of the box, bolted it to the airplane, signalled for start, and then flown an official flight in a contest, first run is a scoring flight - a 500-point scoring flight.

       My suggested procedure, less hubris-filled than above: Take it out of the box, bolt it to a test stand or airplane, put on the muffler,  put about 4 ounces of fuel in the tank. Put on an APC 9-4 prop, sand the TE until it is just blunt enough to safely flip - it is *razor-sharp* as it comes. 5 seconds or so with 240 grit paper should be enough on each side.

    Start the engine with the factory pre-set needle. That will start it at a medium-fast 4-cycle. Let it run that way for about 30 seconds, then lean it out until it is just barely into a 2-stroke all the time. Let it run out the tank, leave the needle alone.  This won't take long, it really sucks up fuel when new. It will probably get richer during your 3-3.5 minute run, and the front end will get *boiling hot*, to the point if you touch the venturi, it will possibly burn you. Let it cool for a few minutes, fill tank, start it up again, and then set it to *just* 2-stroking again. That should require the needle to be closed a bit from the previous run, repeat, until it runs out of fuel. Let cool, do the same thing again, closing the needle to get it *just barely* into a 2-stroke, 4-5 times. Let cool, and your runs should be getting longer and longer, and the front end less and less hot. Thats the friction going away as the plain bearing breaks in.

    After 4-5 runs, fill tank again, start again, lean engine until it just sags lean, then back off 3-4 clicks, until it gets richer enough to give a distinct drop, but still a fast 2-stroke. It should hold that setting, or get richer, if so, good to go. Note also that your fuel consumption will be much lower by now and the front end should not be getting as hot. If it is OK, and stays constant or richens slightly, go fly it. The fuel consumption will stabilize to teh point you can predict what the run time is, it will take around 3 ounces of fuel for a full stunt pattern.

    The starting setting for every flight should be - start engine, lean until it sags, back off to peak, then 3-4 clicks of the needle richer. It will tend to richen up in flight for a while, but then be stable. If it is consistently too fast at that setting (likely), then you can back it off one click a flight, as long as you stay in a 2-stroke. If it is consistently too slow (not likely), then you can try a few clicks leaner, but never "over the top" lean - not because you will damage it, but because it will get even deader in the maneuvers.

   If you have to richen it up all the way to a 4-stroke to get an acceptable speed, then add an air filter or panty hose layers over the venturi.

    The tank should be mounted so that, from the top view, the outboard/right edge of the tank is no more than 1.5" from the centerline of the engine, or the base of the mounting lugs on a profile mount.

   The intent is to run the engine in a medium 2-stroke in level flight and have it lean out slightly in the maneuvers. It is not intended to run in a 4-stroke or a 4-2 break with a 6" pitch prop. It will, but you will have a lot of problems if you try it and give up performance.

   I wouldn't bother with the 5% fuel, us the 10%. 23% is way more oil than necessary and will eventually cause a varnishing issue, but it will take a while.

 Cautions:
Do not take the head or backplate off for any reason. The backplate screws should be just snugged up, do not crank down on them or you will crack the corners of the backplate. If you need to, post back or PM me and explain the situation
Do not grind or drill anything, and don't let local experts tell you it needs to be ground on or drilled.
Do not run it with no muffler or "better/lighter muffler",
Do not modify the muffler
Do not replace the spraybar with a "better" spraybar or front-needle system
Do not listen to any flying buddies who might rush up to you while needling and richen it up because "your are going to BURN THAT UP!!!!"

  The engine does not need to be modified in any way, for any reason, dead stock it probably has the best run characteristics of any engine you have ever had, and doesn't usually need any "tweaking" beyond what is above. If not, let us know.

     Brett

     Great post Brett!

      Frank McCune

   

Brett ,
Thank you very much for a great detailed instructions on breaking in my La25 .
I will follow it step by step as you posted . Sounds simple enough to follow .
Yes that is way easier than when I broke in my Fox35 and OS Max35 back in the 70’s !
If I do have any problems I will let you know .
Thanks again !

  You are quite welcome. To be honest, you probably don't need to break it in at all, or at least not with ground runs, at least for reasons of safety/damage - IF you could be certain of your needle settings.

   All this break-in does is give you some margin, if the setting is wrong, you can fix it, not so in the air. But mostly, it will stabilize the fuel consumption enough to give you some idea how long it will run. The run time from completely brand new straight out of the box, to after 25 flights, is something like *a factor of two*. You will be packing the tank full and still not make it on the first flight, it will get slowly better, and then, all of a sudden, its is running 12 minutes.

      There is a lot of information about running ABC engines floating around. Some extreme measures are required on super-tapered ABC racing engines, like, lean it down hard as fast as you can screw in the needle, to the point of sagging, to get it hotter, faster, to expand the top end and loosen it up. This is absolutely not required for these engines, they are very mild economy sport engines, they don't have the sort of screeching tight top end fit, you can treat them almost anyway you want and it will be OK. They are also not a McCoy 35 or Fox, that (while not fragile, particularly the Fox is pretty durable), so you will not hurt them by running them too hard nor is hours of run time required.

    Brett

On the off chance that you may doubt Brett -- his advice on the 25LA and the 20FP basically carried me through Beginner and Intermediate, and served me well with the 46LA in Advanced and Expert.  He knows these engines.

May I offer a slight caveat for those who might not be familiar with the OS Max FP series of engines?  There are two types of engines in the OS Max FP series.   The early ones have iron/steel piston/clyinders and the later models have either ABN or ABC (not sure).  Obviously, the two would require different break-in procedures. 

Fortunately, you can tell the iron/steel engines from the ABN engines from looking at the outside of the crankcase.  With the glow plug pointing up, look at the crankcase on the side opposite the exhaust/muffler.   The ABN engines have three cooling fins, one just above (1/16" or so) the bolts for the muffler, one even with the muffler bolt and one just below bolt for the muffler.  The iron/steel engines don't have these three cooling fins.  Also the iron/steel engines have a distinct vertical crease in the crankcase from the lugs to the bottom of the fins for the bypass and the ABN engines are more rounded.

Judging by Ebay, OS produced a lot more of the iron/steel engines.

I once asked Brett if the iron/steel ones were equal to the ABN (specifically the .20s) and if I remember correctly, he indicated the ABN FPs were the way to go.

Brett,

Thanks for the break-in guidance.   I bought a new, in the box FP .20 last year, and knowing how to break it in, takes away a lot of the fear of ruining a new engine during break-in.  Also, it helps to know the crankshaft bearing gets stinking hot the first few runs.  Without that knowledge, I'm sure I would have thought I had ruined the engine.

Joe Ed Pederson

Brett ,
I will be test running/break in on an engine stand . I prefer not breaking an engine in on a plane if possible .
I just want to make sure I don’t mess the engine up . I did have a flying buddy tell me not to run slobbering rich like the older cast position engines I had in 70’s ! I won’t try any major stunts with it but will see how it runs with a wing over or loop and go from there after 4-5 tanks on a test stand . If something is set wrong I don’t want to loose a plane while breaking an engine in Up in the air !
Thanks again for all your help !

I am using quality , fresh fuel .
Thanks again for your help !
I’m hoping to try running the engine next week if my back gets better .

Brett,

as usual thanks for your tips on how use correctly an OS 25 LA.
I use your 20FP setup on my Skyray and I'm very happy with it.

After that, as you say the RPM setting on ground for the FP, may you say the numbers correct setting on 25 LA. Just to be sure to reply the same numbers and not misunderstand about "just barely" 2 stroke etc etc.

     I am hesitant to give specific values, and the "setting curve" is something I will make a clearer explanation of when I get some time.

     For *my* 25LA, at sea level, using Powermaster 10% fuel and an APC 9-4 prop, it will spin about 14,200 RPM peaked out lean, as fast as it will go. It will be the richest possible 2-stroke (that is, its firing every cycle, and one click richer will cause it to start missing cycles, it about 13,200 rpm. I don't normally set it for flight with the tach, but, on the occasions I have checked it, the launch RPM is 13,400-13,500, which is a "rich/medium 2-stroke".

    Of course, the desired RPM is dependent on a lot of other things, like the drag of the airplane and how much wind you have.

    What I normally recommend is to start the engine, peak it out lean, as fast/lean as it will go without sagging, and then open the needle until you hear a *distinct* drop in the RPM, let's say "distinct" is 3-400 RPM. For the standard OS front needle, that's usually about 5-6 clicks open from peak. For the stock 25LA rear needle, that is maybe 3 clicks open from peak. This will give you more than the 13,400 I mentioned above, meaning, you might have too much speed, but at least you can get through the flight that way. Then, adjust depending on what the airplane needs.

     If in any of this, you drop into a 4-stroke, either in level flight, or certainly on the ground, you have probably gone too far. If it is still too fast and you have to needle it down into a 4-stroke to get a decent speed, then, you have some options, but most likely, you have put it on too small an airplane. Depitching the prop (possible with A LOT of heat on the APC), trimming the prop tips, or getting a $45 Australian graphite prop and depitching that, restricting the venturi with air filter/panty hose.

     In all cases I have found, you want it and can tolerate it going a lot faster in terms of lap time than other engines, particularly 4-2 break airplanes, because while it might be fast in level flight, it should just barely pick up in the maneuvers, and never do anything abrupt to mess up your timing. The effect is like it goes into slow motion during the maneuvers, even though it isn't, because it is so predictable and smooth. *This is why it is such a good stunt engine*, people used to spend decades trying to get that to happen reliably, failed most of the time, and the rare days it worked like that, they won the contest.

   The beauty of these systems is you have to know *absolutely nothing* about stunt engines to make it happen with a 20FP or 25LA, other than simple instructions and *leaving it alone*. Most "engine experts" would  - and frequently do - screw it up with their first action. Beginners follow the directions and go learn to fly.

    Brett

 
 If it is still too fast and you have to needle it down into a 4-stroke to get a decent speed, then, you have some options, but most likely, you have put it on too small an airplane. Depitching the prop (possible with A LOT of heat on the APC), trimming the prop tips, or getting a $45 Australian graphite prop and depitching that, restricting the venturi with air filter/panty hose.

    Brett

Is making the lines longer a viable option if the model flies too fast when the engine is running in the sweet spot using an APC 9 x4?

Joe Ed Pederson