Whatever old thing lying around. (Just kidding.) I do know people like that though, and my brother is one of them. Then he wonders why engines don't play well with him....

I have a bunch of engines, so the answer varies. I don't remember the NGK specific numbers right off the top of my (old age) head. Besides heat range, there are two basic variables in the plugs for most of our engines; sealing surface and hex size. The sealing surface is either taper seat or gasket, and the hex is either 5/8" or 13/16". Hex size is important for engines running the newer ignitions with a metal cap as they only accept the size they were designed for, and sealing type is important on most engines. A Homelite will accept either sealing style plug though, and with the magneto, should accept either size hex as well.

I just looked at your pic closer. As I recall, that's a correct number, but there's something wrong with that plug. Either it had a mistake in manufacture, or the connector got broken off.

Of course, make absolutely sure no matter what that you use a resistor plug, especially with that unshielded magneto. (NGK's with an "r" in the number are resistor, as are most brands, but if in doubt be sure to check.) Sparkplugs.com is a good plug research site.

AV8TOR