First, tune it by sight and power. Just tune it so that its neither lean, nor rich. Then slowly lean it until you've still got a stream of smoke when you drive and it doesn't stall when idling or while during WOT runs. Then just use the water on the cooling head trick to see if you're running to hot. If you're running to hot, richen by 1-hour. Then just keep checking the temp that way until you buy a temp gun.

Hope that helps