The Elusive NA-12 Spark Plug

Racing K Models

The Elusive NA-12 Spark Plug

Postby hennesse » Sat Mar 04, 2023 5:43 pm

It took me 5 or 6 years of looking to find one of the NA-12 spark plugs that were provided with many of the racing models. The brochure on the Competition page shows that the 1953 KR and KRTT (but not the KRM) "ADDITIONAL EQUIPMENT at no extra charge: two Champion NA-12 spark plugs and one spark plug wrench".

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Champion NA-12 and friends
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The Champion NA-12 has a recessed side electrode just like the Harley #8 32306-61 plug used on 1961-1971 Sprints. There's a hole drilled in the last two threads, with a pin (side electrode) inserted. They look almost identical, except the NA-12 has a shorter insulator. The markings on the other side are Champion followed by Reg U.S. Pat. Off., and then the letter A.

The NGK BR8ES plug looks almost identical to the Harley #7, which also was used on 1961-1971 Sprints. However, the BR8ES is a resistor type.

My 1954 KH has KR #7 heads that take these long 3/4" reach plugs (plus some other KR goodies). I wasn't sure which plugs to use, so I gave the NGK BR8ES's a try, and they seem to work just fine. And they're a lot cheaper than buying the Harley plugs on eBay.

The NA-12 was for sale on eBay in the United Kingdom. The plug was cheap - like $5 or $6. But the seller wanted an outrageous amount to ship it over here in the U.S. I looked up some prices on the Royal Mail website, and got an idea. I emailed Ken Lee, a Henderson buddy who lives in the U.K., and asked him if I could have the plug shipped to him (a couple of pounds sterling), and then could he ship it to me, at considerable less cost than the seller wanted.

Ken emailed me back that he was willing to do this, but the eBay listing now showed that the plug had been sold. Downhearted, I read through the rest of his email, only to find that the plug had been sold to a guy in the U.K. - named Ken Lee !!!

He shipped it to me via Royal Mail "economy package" at a very inexpensive cost. Little did I know that "economy package" meant putting the package in a rowboat, and pushing the rowboat eastward into the Atlantic ocean. It took more than a month to cross the pond, but now I'm the proud owner of a NA-12. Now all I need to do is find another one, so I'll have a matched pair. Check back in another 5 or 6 years.
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Re: The Elusive NA-12 Spark Plug

Postby wz507 » Sat Mar 04, 2023 10:29 pm

Below is a table of ¾” reach 14 mm Champion spark plugs that provide a variety of heat range – this specific plug collection certainly tends toward the cooler end of the spectrum (53s are coolest, 59s are warmest). As Dave noted in his comments, many of these too are quite economical compared to vintage Harley or other plug offerings. I am personally partial to the 5/8” hex size as the room under a stock KH tank is tight and a small 5/8” socket allows easy access to the plugs.

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