14mm = diameter of threaded piece and hole into which it's screwed. 21mm = diamater of hexagonal section with which you screw it in.
Therefore your holes need to be 14mm and your tool needs to be 21mm.
Got that?!
How to change spark plugs?
Apr 19, 2005
23 Replies
Ask Michael Jackson.
Si
The message from James Dore contains these words:
She ain't going to like that.
Make sure you adjust the gap if needed prior to fitting as many people assume they are factory set ( not true and needs can vary )
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