If your injection is working correctly, it doesn't need to be richned up!
Don't you think you put more stress on your engine, say the last lap of a muddy race after it's been hammering for 2 hour or when you and your buds have been ripping up the earth all afternoon?? The manufactures have tested the oil mix and know what to put in to keep them running.
Keep the RPM and load, (lugging it), to a mimuium unitl every seats in and the toleraces ease up and it'll be fine.
If you start screwing with the mix, you'l just load it up, them you'll have to clean it out by reving the BE-Jesus out of it, the spike in RPM will just hurt your new motor.
I don't even worry about a new motor, I've had them totalal rebuilt, ran @ a few minutes and raced. (I have dump my gear oil when I get any gear/crank/clutch work done, to get rid of any junk left in there.
All scoots, (2 smokes) are needle bearing design, they spin easy, the cylinders are for the most part hardned, (chrome plate, etc) so they are tough.
Keep the filters clean and dirt out of the engine and ride, don't loose sleep about how to break a new one in!
I've yet to find a, "off the assemble line" motor really tight, most times they are in the middle of the tolerences. If you have your cylinder bored, (old style cylinders), you had to watch piston/cylinders spacing. You gotta check the ring gap when you do a rebuild, but I've only seem/heard of a few that were too tight ring gap or wrong piston.
Joe