K and Early Sportster Delco-Remy Regulators

Harley-Davidson purchased 6-volt voltage regulators from Delco-Remy through 1964, the last year of 6-volt systems.  The 1952 K model inherited the two-unit regulator from its smaller brother, the Model 125. The K's, early Sportsters, Models 125 and 165 continued to share regulators through the late 1950's until the Model 165 was discontinued. The regulators for these models are all 6-volt, "A-circuit", negative ground, two-unit (cutout relay and voltage regulator) models. In contrast, many of the big twins used a three-unit (cutout relay, voltage regulator, current regulator) model.

Delco-Remy regulators may be identified by examing the right mounting "foot" or nearby areas. Early models had just the last three digits of the D-R model number (e.g. 307 = 1118307). Later regulators have the Polarity (N or P), voltage (6V or 12V), three-digit model number, and a manufacturing code stamped in that location

Note that most automobiles, trucks, and farm tractors in the 6-volt era used POSITIVE ground. These regulators will not work correctly in a negative-ground motorcycle!  See the "Regulator Polarity" sections in 1R-115 and 1R-116.

Harley-Davidson to Delco-Remy Cross Reference

[1] The part number reform of 1951 changed this to 74510-47. However, a box marked 31700-47 would be a D-R 1118283.
[2] The 1118200-series of regulators do not have adjusting screws, adjustments are made by bending tabs inside the unit - See, 1R-115.
    These were used on the Model 125 (Hummer-series), and were superceded by 1118307 - probably in 1952.
[3] Although the size and cover mounting of the regulator changed, Harley did not change the part number.
[4] The 1118300-series of regulators do have adjusting screws - See, 1R-116.
[5] This larger unit was easier-to-service. It appeared in 1955 and was probably used through 1960.
[6] This unit probably appeared in 1961 along with the Model 61 generator.
[7] The cutout relay and voltage regulator actuate at much lower voltages to provide lighting at lower engine speeds and not burn up the
    light bulbs.
[8] See this Harley document for additional info.

Harley-Davidson Shop Dopes

Harley-Davidson Specifications

These Harley-Davidson specifications were taken from the 1959 and 1966 Hummer Service Manuals, which include the regulator specs for all Harley models. Note that in most cases, these specs differ from the generic Delco-Remy specs. Some regulators may have been used on other type of equipment besides Harley-Davidsons.

Delco-Remy Specifications

Finding the specifications for each regulator will require going through the 1R-18x Delco-Remy Service Bulletins, then looking up the testing/setting procedures in the appropriate 1R-11x Service Bulletin. We've recapped the specs below. Before testing and adjusting a regulator, please read the Service Bulletins in their entirety. They contain important notes, such as test setup, adjustments for operating temperature, and other important stuff.

Delco-Remy Documents

Delco-Remy Service Bulletins and other documents are important references for testing and setting regulators - not only for our precious K models, but also for antique cars, trucks, and anything that uses a D-R regulator. The 1R-11x Service Bulletins have been available on the Internet, but they reference the specifications in the 1R-18x bulletins, and nobody could find those. Recently, I had my 52K generator serviced at Arlington Armature, and we tested/adjusted my newly acquired reproduction regulator - it was set way too high. They had the 1R-180-series bulletins in their archives, and agreed to copy them for me. Now you have them too.
Many thanks to: Mike at Arlington Armature, 7215 Lockport Place, Lorton, VA 22079, 703-912-7770