ORIGINAL: ameyam
ORIGINAL: CGRetired
My reasoning there was that I had recently ran an engine in on my front lawn (the plane was tethered to the ground and I ran the engine up through at least two tanks of fuel.. maybe three). My technique was full throttle with blubbering rich HS needle setting, with occasional excursions to lean for about 10 to 20 seconds, followed by blubbering rich settings.
CGr.
CGR, thanks for getting that out of my head. I have 2 engines -a 55ax and a 75ax, from my trainee days that have recently given me a lot of problems. I was told that this was becuase, like you, my instructor didnt run these in properly on the ground but rather, he set them rich and flew with them directly (no nose up flights though). Now that you have mentioned that this is also as less desibrble but acceptable practice for 2c engines, it will put mind to rest that I did not do wrong in not objecting to his impatience with the engines.
For the record, we too run the engines very rich and full throttle with intermediate leaning for 10-20 seconds like you said and I will ensure we do this with all further 2c engines
Ameyam
Running a new engine rich only has one purpose, to ensure there is lubrication, In a ringed engine the edges of the rings must wear down and at the same time the edges of the rings bite into peaks of the honed cylinder walls.
An engine doesn't have to be run to be broken in! The only thing that's going on in the break in process is bearing surfaces are getting worn so they have less friction - and cylinder walls which need microscopic peaks and valleys for the entire LIFE of the engine need to have a place for oil to stay on the side of the cylinder wall to lubricate the ring going up and down.
And yeah, its the same on a VW lol get a clue, F1 race car or our model engines, Don't think you have to fire and run an engine to "break it in" - that's just how we do it - but the "breaking in" process has always been about "seating" rings - and seating rings is NOTHINGMOREthan the edges of the rings cutting into the peaks of the honed surface of the cylinder wall, leaving the valleys to hold the oil. There's nothing magical about it - and these days with machining advancements an engine is virtually broken in from the factory.
Just keep the engine blubbering rich allows the edges of the ring to wear down the microscopic peaks of the honed cylinders.
And by the way, in my investigation OS engines over the past 20 years have the worst tolerences for sloppy piston / cylinder tolerences. It would be interesting to hear if other people have found this to be true.