can anybody give me a setup on the mt12?

HSN = 5 turns out, then start leaning 1/8th at a time if needed.
LSN = 3 turns out, then lean or open as needed to get at least 30 seconds idle without engine clogin to the point of dying, it should hesitate a little after 30 seconds but not die. To do this, let engine idle then press full throtle for a second or two to clean it out, then check the 30 seconds idle.
Mid Needle = flush with carb body with slot for screwdriver pointing the fuel inlet, then DON'T EVER TOUCH IT AGAIN.

AFM

What characteristics would an overly lean bottom end give? I'm having some setting issues and I could use some help. Thanks

Try this tips on tuning engines. Best guide I've seen.
Good Luck
AFM

http://www.teamtrinity.com/tech/nitrotune.asp

http://www.teamtrinity.com/tips/nitro.asp