[Spridgets] New Problem

[Frank Clarici]

Here is one for the record books.
Spark plugs, still clean and slightly tan after a 15 mile run, they stop 
sparking!
Replace plugs, go 15 miles, plugs stop sparking.
OK, if they were black, I could understand that the carbs were way too 
rich and the plugs fouled out but the plugs are fine, if not new looking.
Bead blast the old plugs and they still do not work.
Put in new plugs and all is fine for a few miles.
WTF?
This is not on my car, but it is a Sprite and if I ever have this 
problem, I would sure like to know what causes this!!!
Any ideas?

-- 
Frank Clarici
Toms River, NJ