Breaking in a Stihl 500i, any tips?

That's what is good about these systems vs automotive EFI. They make few assumptions about fuel quality and supporting equipment. They simply tune for best performance under load. Which is exactly how us humans would do it in most circumstances.

If something was off in the fuel that made it run worse, the computer fiddles with the fuel delivery to improve performance. So adding oil to the mix, would likely cause it to add fuel to the incoming charge, which in turn actually delivers even more oil. An automotive system assumes the fuel is of a certain octane rating or better, and will perform at a fairly narrow range of air:fuel ratio. Some don't even measure the incoming air charge and assume the engine is moving a set volume of air for any given RPM. Get outside of that curve more than what the narrow band O2 sensors can read, and it's game over.

 

But is that actually necessary on an engine that has a plated cylinder bore? The surface finish of a new nikasil plated cylinder for a saw, bike, atv, cycle, etc. is a very different thing than a honed cast-iron sleeve like you'd find in most automotive engines. We are starting to see plated bores in high-end automotive though. BMW, Alpina - I'm not as familiar with others, but I'm sure BMW isn't the only one doing it now. It's a big reason why you don't see oversize pistons available for theses engines, as boring/honing would ruin the cylinders as designed.

The legacy way of breaking in engines was to put them under full load for several short intervals, as soon as the cam break-in was complete, be that in-chassis or on a dyno. But "breaking in" something that has plated cylinders and roller/ball bearings has to be quite a bit different (if it's even necessary) than cast sleeves and journal bearings. Just like it's not really necessary to break in a roller cam valvetrain like we would for flat-tappet setups.

For saw engine break-in, I say use good mix, nothing special. I like 40:1 with my stuff, I wouldn't go 32:1 or anything like that just for break in. Keep the Rip Em's reasonable, like the manual says, and always run it at full throttle in the cut. Babying the throttle probably isn't the best for it, and I'm cynical on if idling it for a tank or seven is of real benefit to the engine. (On board with the Beer and BS though!) I've seen timber cutters pin the throttle and limb a straight trunk, maybe we hold off on that for a few tanks. But I doubt anyone is running a firewood saw in that manner.