You may need to clean the carburetor . They are easy to service and quite often no parts are needed if you are careful taking it apart. The idle mix screw should be 1.5 turns from seat.
Alright, i plan on running it this weekend in a 55gal drum to tune the carb, i just rebuilt it when i started having the problems. its been difficult to get this thing tuned. if it helps any i am in Arizona, would the altitude have any effect on the idle mix screw?
The idle mixture screw will end up 1/4 either way of the 1.5 setting. Are you sure the points are good and adjusted along with the timing ? Is the compression even on all 4 cylinders ? The exhaust manifolds did have a problem with the #4 cylinder getting some water when they started to get rusted and had an internal leak.
