Never tune by temp, tune for optimum performance across the operating range, but the **average** operating temp for a .12 engine is between 210° and 260°.

If you don't have a temp gun, use the "spit test." Water boils at about 212° (excepting people in high altitudes. ) When the engine is up to FULL operating temp, drop a dime-sized drop of water on the top of the engine head. It should boil off in 3-5 seconds, if it sizzles and pops like a fried egg, it's very likely you're running too hot and should enrich the fuel mixture or determine other possible causes of the overheating.