The only difference is the "S" has a tapered seat, the "C" has a gasket and joint seat. Won't seal correctly if you don't use the correct one.
GAP .030"
My lawn tractor is 12V, but I bet there are 6V ones also.
no
Yes
your dum
Rc12yc
A champion RC12YC spark plug is 14mm thread diameter. The torque for this size is 18-22 foot-pounds (25 to 30Neuton·meters)
yes
I have interchanged them and it seems to work. Everything is the same apart from the hex wrench. The hex on the RN12YC is 13/16" (20.6mm) and on the RC12YC it is 5/8" (16mm).
Rc12yc
Champion 3071
.035"