Spark Plugs #4-5: XL 1979-1985




- Spark plug by Autolite
- fits Sportster 1979-1985
- porcelain / steel
- thread: M14 x 1.25
- thread length: 1/2 ”
- wrench size: 13/16 ”
- connection thread: M4
- manufacturer-code: 4123
- replaces Harley-Davidson part number HD 32301-80
- gross weight: 60 g
Autolite Spark Plugs
Autolite is one of the classic American spark plug brands, made by the oldest American manufacturer. Recommended for magnetos.
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.
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Have any questions?
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