Carby checking spark plugs with stock carb?

[willfargo]

I remember reading a thread a few weeks ago about adjusting air fuel mixture and checking the spark plug to see where the mixtures at. white is too lean, black is too rich, nice tan/brown is just right. Im not sure if this was for the stock carbs or just the CNS style adjustables, but i just pulled my plug (still breaking in, gone through 1 gallon of fuel) and it is BLACK. pretty serious amount of carbon on the ground electrodes, but the center electrode looks just fine. is this because im running 16:1 mixture for break in? is there even an adjustment on these tiny stock carbs for air fuel or is it just idle speed?

also, i installed a boost bottle on the engine, and checked for air leaks. solid, but my idle rpms are pretty high compared to what they used to be, and adjusting that idle screw doesnt seem to do anything

 

[double trouble]

you're o.k.

The adjustment is for idle only . It doesn't do much either. Your mixture is double what you will run after break in. Do not worry about an oily plug yet. As long as the motor runs good.
If I had it to do over again on break in I would run full synthetic oil or at least a semi that meets jaso fd or a full synthetic that is tc . Remember to vary speeds a lot and try not to keep the throttle wide open. Standard break-in procedure.