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Spark Plugs
Spark Plugs #2: IOE, Flatheads and Knuckleheads

Spark plug by Champion

Item №
  • fits IOE models 1927-1929, Singles 1926-1934, Flathead 1929-1955 (exc. K-models) and Knucklehead
  • porcelain / steel
  • thread: M18 x 1.5
  • thread length: 1/2 ”
  • wrench size: 7/8 ”
  • connection thread: M4
  • heat range: manufacturer-code D16 corresponds to HD-code 2
  • replaces Harley-Davidson part number 32304-09, and 37-09B
  • gross weight: 80 g

Champion Spark Plugs

Stock replacements since decades with proven performance. Excellent value.

Spark Plug Heat Ranges

Harley spark plug heat ranges are marked by numbers, from 2 to 12. No. 2 is the hottest plug, no. 6 would then be a relatively cool plug. The coolest plug used by Harley-Davidson is marked 10R12A. Double numbers characterize multi-range plugs.

With older motors, it was not uncommon, that you achieved an optimum with plugs of two different heat ranges. Unlike the well known prejudice implied, you had to choose cooler plugs for the front and hotter plugs for the rear cylinder. On later Harley engine designs, heat distribution is balanced to such an extent that you should not have to rely on those tricks anymore.

net price*
* United States of America: Tax free shipping. Please check your local import fees.
In stock. Ready for immediate delivery from our Würzburg, Germany warehouse
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