Dual plug head

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Dual plug head

Postby Emerica1975 » Tue Sep 27, 2022 10:09 am

I found this head at a swap meet last weekend. It’s a cool idea. Not really sure of the advantages of it but cool non the less, and I thought I’d post a picture of it. I love finding parts like this!!
7A8ADD1A-FAA1-44C0-81C2-E1BC7DA79245.jpeg (203.49 KiB) Viewed 324 times
73261398-A6AC-4123-BD54-E47065AF3708.jpeg (186.54 KiB) Viewed 324 times
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Re: Dual plug head

Postby pumpguy » Tue Sep 27, 2022 10:51 am

Back in the days of leaded gasoline, a common problem with 2T engines was spark plug whiskering.

Under certain conditions, a fine whisker would form across the spark plug gap, shorting out the plug. When this happened, the engine would stop. You then needed to pull the plug, flick out the whisker, replace the plug, and be on your way.

With a 2nd plug already fitted, it was a simple matter to switch the lead to the other plug and be on your way.

Another reason for 2 plugs was to have both plugs firing simultaneously. This could be easily accomplished using a twin lead coil from a Harley big twin.

And still another reason was a central spark plug was thought to be a better location. In that case, the back tapping was just plugged and not used.
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