spark plug removal

[kudzupammi]

I have all 3 sizes spark plug wrench but non are fitting and turning the spark plug. when i look into the opening it looks round not octoganol like the wrenches. have even tried the metric versions but they don't grip it either. what can i do?

NEVERMIND! finally got them out.

 

[Rivets]

What engine is it on? Mattis tiller or Kubota M-series tractor. Makes a difference.

 

[chance123]

My guess is that you can only "see" the round part of the plug, and the hex part is below what you can see. Take your 13/16 plug wrench and wiggle and turn it to see if it drops down on to the hex. If that doesn't work, try the same with your 5/8 plug wrench