.040"
.40
the gap for a Harley plug on a 88c.i. is 30
.040
.038" to .043"
.040 or 40 thousandths
.040
.037"-.043" using any spark plug gap gauge. I have a 93 heritage softail classic and that is what is recommended.
Use a dime to gap the plug. If u haven't got a dime use two nickles
The spark plug gap for a 1999 H-D (Harley Davidson) is .032 to .036. The actual gap depends on the brand of spark plugs.
The factory plug is HD PN 6R12- This is also available in the gold series plug. The factory plug is HD PN 6R12- This is also available in the gold series plug.
Twin Cams take a 12mm thread diameter plug. All Harleys with electronic ignition require a .040 plug gap.