Hopefully it's the 6R12. Never thought to ask that hoop!:s
hd-6r12you said the plugs were hd but what plug number are you using.
I go with .040 and it seems to work for me, but I'm by no means an expert, just been lucky I guess. :sMy manual also says .038-.043 in. So would you gap at .040 or what exactly?