spark plug fouling

[series1gtv]

I recently adjusted the delivery screw on my spica 69gtv this adjustment was to make it slightly leaner. This fixed my slight backfiring problem but now I'm having trouble with it fouling plugs. I'm using BP6ES NGK plugs they seem to work good except for the #3 cylinder which tends foul. Any ideas why? Which way is more likely to cause oiling of the plugs rich condition or poor?

Thanks for yr help
Jeff

[Alfa]

My 1750 Mk 1 is the same, plugs become horrible, but car seems to run great!

[series1gtv]

I seem to have cured the problem by replacing the points ignition with an electronic ignition. The really nice thing about it is that unless you remove the cap and rotor or see the box you would never know.