There is a tendency for everyone with BLACK plugs to automatically go to the carb and ignore the other engine design parts which effect the actual combustion adjustments of these engines.
The CARB isn't the only source of "HOW MUCH or HOW LITTLE GAS".
VALVE GAP and TIMING also effects this.
PROPER GAP of the POINTS and PROPER SETTING of the POINTS is also necessary.
Quite often the CAMS a TOOTH OFF will cause this (case in AU at this time) and I thank the owner for the pics of the points settings.
I offer the last from what you said that they have always been BLACK since the rebuild.
GOOD LUCK MY FRIEND...................lm
casamere wrote:They have been black ever since the rebuild so my thought are still with the carb but will not do any harm to check the valve clearance.