sizes of spark plug sockets

I've seen and used three sizes.

The Autolite 4164 that some people run on their Harley's is 11/16. Older Harleys were 13/16 and the ones since 2000 or so are 5/8. Other people run NKG's that are 18mm. 18mm and 11/16 are usually close enough. I think 3/4 plugs are mostly lawnmowers and other small engines.

Don't you love standardization?

So that's five.

That would be nice. Surely two sizes are enough. Anyhow, i had looked it up and the sparkplug for the scooter is 5/8, but the 11/16 socket I had worked.

I also have a set from 10 or 15 years ago I've never opened. I figured it was cheaper to buy a whole extra set than buying good replacement sockets every time i ruined or lost one. But I've not taken off the shrink wrap. It has 5/8", if I'd needed it.

--------------------------------------------------------------------------------------------------------- Late model Ford V-8's use plugs that take a 9/16" socket. ======================================================== Remove the ZZZ from my E-mail address to send me E-mail.

So that makes 6 sizes?

And what size socket fits the 8mm plugs used in the old Honda 125 twin?? If I remember correctly it was 13mm or 1/2 inch on the original plugs, but that was a long time ago. I think NGK er9eh. / Champion

Add 1/2 inch for 8mm thread plugs - so 7.

Absurd.

I'm not 100% sure, but when I changed the plugs on my Farmall M tractor, I'm pretty sure they need a 7/8" socket. I know I had to use a deep socket because I did not have an actual "spark plug socket".