07 road king, put a new set of spark plugs in got about 300 miles on them and they still look new, just a little carbon showing by the threads, porcelain still white. wondering how log it takes to see any color...for that rich/lean reading...

 

you should see some color by now, what mods have you done

 

supertrapp exhaust SE air PCIII....leaning a canned map for 20 discs to my 16 discs...runs great but the 20 disc map was bad on gas mileage,after tweaking map im getting about 38mpg and no color on new plugs...

 

Reading plugs (or doing a plug chop as it is properly called) is not the result of "running" the plugs normally for a while, but is instead taking a new set of plugs, installing them, then running hard through the gears at WOT, and while still under load pulling the clutch and shutting the ignition down at the same time, pull the plugs and 'then' reading them.

Anything else it arbitrary and will not provide the proper readings for jetting/tuning.

 

+1 about shutting down under load (well quickly after) just before checking plugs. Running hard through the gears and WOT not so much, unless your drag racing.
What you should be mainly concerned about is running too lean or too rich under normal operation.

 

Yup ... there are certainly different ways to the chop.
And lots of information on how to do it, can be found on the 'net.
Most important is to not be jockying the throttle about during the chop run.
That and the fact that when at WOT you are looking at the main (not the needle taper) is why I say WOT.
One the main is right unless you have some sort of crazy taper, you will be safe.
Most of us are just looking for the right size mains/ensure we arn't too lean and damaging our engines.
But .... you will need to find some decent fuel (racing) to get a good reading, as (IMO) most pump unleaded won't really provide a good reading.