PROPER break in happens in the first gallon (or way less). You need to seat the rings- fire it up, get it warm enough to run good, then go for it! Run it up with a light to moderate load and heavy throttle, then at around 20-25-ish, pull the clutch and slow it back down. Do this a dozen times, and you're about done with "break in".
After that for a tank or two-
You should not run the engine too slow, and you should vary the throttle a lot, including WOT runs. DON'T let off the throttle and slow down with the engine. Pull the clutch. When the throttle is closed, there's little lubrication going to the rings.
Finally- If you must- run it at 16:1 for a tank, then mix your fuel at 36:1 or 40:1 (50:1 synthetic) and figure out your mixture. You want a light tan to dark grey plug,