Running an ABC (or ABN) engine rich will ruin it. So if anyone has used those OS instructions, as far as I'm concerned, they should write to OS and demand a replacement engine.

ABC engines have an Aluminum piston in a Chrome plated Bronze sleeve (ABC), or Aluminum piston in a Nickel plated Bronze sleeve (ABN) which the OS's actually are.

Because of the different rates of expansion of the piston and sleeve, the sleeve is bored to a taper making the piston/sleeve fit "squeaky" tight at top dead center. (Sometimes they're so tight it's difficult to turn them over when cold.)

IF you run one of these "4 cycle" rich, the excess oil/fuel will not allow the engine to get to operating temperature, and the piston will rub against the sleeve causing excessive wear. The end result will be too little compression for a good, powerful engine.

Proper break in? Tune the engine until it's completely 2 cycling (at full throttle obviously) but not peaked, and run it for 3 to 4 minutes. Shut it down and allow it to cool enough to touch the cylinder head.

Restart the engine and repeat. Run through at least 2 to 3 tanks this way, then you can fly it. Do not lean the engine much beyond the break in setting until you've run a couple more tanks through it.

Of course, you never run an engine at "peak" RPM, always at least 300 - 400 below peak. (They lean more in the air when the prop unloads.)

You never set an engines primary needle valve at idle though. You really can't determine it's high end setting, rich or lean, unless you're in the "high end" (full throttle).

Setting the low end, or idle mixture is done at low throttle; set with a second needle valve or an "air bleed" screw depending on the engine. Changing the idle mixture will change the high end setting a bit, so be sure to re-set the high end. (But high end needs to be set first, then low, then recheck high end.)

I know it's difficult to know what "rich/lean" sounds like without knowing what it sounds like, but I don't have a sound file, sorry.

But at Full throttle (as I mentioned), a lean-ish needle setting will sound like a continuous fairly high pitched 'whine'. Four cycling sounds like the whine is constantly breaking into a 'burble'.

Nyee-ee-ee-ee-ee-ee-ee-ee.... is as close as I can "write" lean.

Nyee-ee-arl-ah-ee-ee-yahl-ee-ee-ahl-abl-yee-ee-ee... is as close as I get to "rich".

You really have to sound it out a couple times quickly, but I hope it helps.

Good luck, and the easiest way to do this is find help locally if possible.
Dennis-