Face it.
1. A break-in is much safer and easier to do on the ground and at your immediate control than in flight; obviously not at your immediate control.
2. A break-in is much safer and easier to do, with the engine mounted in a test stand than with the engine mounted on your new plane.


Ok let me get this straight ,your saying that a engine is safer in on a bench than in a plane , does the bench have a guard on it to prevent you from getting your hand in the prop ??? NO they dont . Are you going to fly that bench? again NO . are your needles harder to get to on the bench or the plane, depends on how you made your setup on the plane. I make mine easy access but have seen a few that was a real bugger to get to so the bench wins this time.
I can't think of one good reason why its safer to breakin a engine on the bench versis the airframe if you have a proper restraint on the airframe , Standing over it useing your legs is not what I call a proper restraint.
So why is it so much safer to break in your new engine on a test stand ???

Other than pissin off your neighbors and creating alot of smoke and oil on the walls of your shop I see no reason to run a engine typical 2 0r 4 stroke on the bench unless you are trouble shooting the engine or just like to play.
BTW if you have trouble starting and running a new engine your doing something terrible wrong. Todays engine are very user friendly and don't require the hastle of yester years heartachs trying to get one to run.

I still say a engine needs a certain amount of load on it to seat the ring in properly and nothing you or anyone eles is going to say thats is going to change my mind.
I do agree that a lighter prop can be used for the initial breakin and even used to fly the plane with .
I have used a breakin very much like the one you have posted all over the place in here on ABC/ABN engines for yrs, since the first one I ever bought in fact, Before I ever heard of you or RCU for that matter. That was a 46 FX and it still runs perfect today, and does those RPM's you say it cant do also *LOL*
But again after a tank or 2 on the ground to get the needles where I want, and up it went. I don't tune for max RPM's I tune to make sure it's on the rich side but still a strong 2 stroke mode and will stay running W/O a dead stick and go from there. I also say that a engine will run cooler in the air, agreed 5.4 degrees F per 1000 feet is all but counts and is not the whole pic, wind chill factor call it what you want but its there when air is moving over and around the engine or anything for that matter.
I think thats why they call these engines AIR COOLED !!! I defy you to tune a engine for 80 degrees F and try to fly it in 30 degrees F weather W/O retuneing the needles don't try tell me air temp dosen't have a effect on both the engines temp and airfuel mixtures because it certainly does. Put some onboard telemetry on your engine and fly it then come back and report where it runs the coolest at ground or air.

WHATS THE BIGGEST CONTRIBUTING FACTOR FOR A DEMISE OF A GLOW ENGINE? or any engine for that matter?