if spica injected, thereis an idle adjust on the thing that looks like a spider on top of the intake manofold. thed one with four vacuum hoses connected and one larger one that goes to the oil vapro seperator. they have an o ring in them that sometimes goes bad and will not allow the idle to adjust.
if carbs, there is an idle stop between the carbs, there is also a carb ballance there too, a little more headache to adjust if you get on it.
I'm not too sure how it comes apart, there should be some info on the board. Mine was still there, but carbs had been mounted. my sons 69 spider has a totally different idle adjust built onto the airbox.