I was on an engine-fitting course many years ago ... there was a magneto type spark plug testing jig and a boxfull of used spark plugs, all kinds of plugs... fresh, stale, black with carbon, .... ones with burnt-out electode(s) an others that looked virtually brand new;
you get the picture
Just half an hour playing around with the plug tester and the boxfull of plugs taught me that yer can't tell how good the spark will be from how the plug looks
All kinds of lillywhite virginesque beauties can give no spark whatever and of course all kinds of burnt-out old things can still have a tune or two left in 'em.
The easiest test in the world is to swap spark plugs - it's crazy not to do the obvious easy diagnostics first ....make it easy on yersel' ... always have two or three good newish spark plugs in yer kit and never judge 'em by the way they look.
restapukin
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