I hear this from time to time:  The OS engines don't need much, if any, break in.  This in regards to the LA and FP engines since they seem to be set up from the factory a *little* looser.  I tend to believe that a proper break in is still beneficial for longer life and consistent runs.

So???

Thanks
Bill <><

Hi Bill

OS engines can't be fitted as tight as an AAC or ABC  engine, the coatings on the inner sleeves are thinner and will not stand a really tight fit, it would peel  the coating off if if were fitted very tight. So.. OS fits the piston/sleeve with a lower angle taper and a close tolerance fit, without much of a pinch fit.
And yes even the looser fit OS engines will not be hurt, and will be  helped by a slower breakin,
The OS engines that are plated with electrolis nickle will benefit from a slower breakin, The coatings are not as hard when you buy a new OS engine with this coating as they are after many heat cycles, Every heat cycle you put on one of these motors makes the sleeve coating harder up thru about 50 runs, this is where the OS benefits from a careful breakin and heat cycling.
Electrolis nickle coatings can take up to 30 hours of heat cycles before they reach the maximun hardness.
This doesn't say you can't run them out of the box, but I think I have shown a good reason not too!

Regards
Randy

Late in on this one, but I HAVE noticed that the first few runs on LA, FP or FX OS Engines are VERY fuel-thirsty, and perhaps a bit fussy to set.

After 4-6 heat-cycling runs (just up to full temperature, cut off, cool to air temp), they start getting nicer and more economical on fuel... Over the next 15-30 runs, they reach a plateau, where they will stay for quite a while, dependably, no fuss, no muss, no greasy wax build-up. (I do the initial runs on a bench, in case something starts to go wrong - if it does, I can yank the fuel line off for a quick stop.)