Technical: Generators
Dave Hennessey, Perry Ruiter, John Andrew, Michael Broad, ‘Dr. Dick’



Five generators were used on the K models and Sportsters from 1952 through 1969. As with everything Harley, there were minor improvements made throughout the years. The Spare Parts Catalogs must be consulted to find every little change.

Volt Model Part # Used On Also Used On
6 Volt Model 52K 29982-52 1952-1956 K/KH; 1957 XL
Model 58 29975-58 1958-1960 XLH, XLCH Big Twin, Servi Car
Model 61 29975-58A 1961-1964 XLH, XLCH Big Twin, Servi Car
12 Volt Model 65 29975-65 Early 1965 XLH, XLCH Big Twin
Model 65A 29975-65A Late 1965 to 1981 XLH, XLCH Big Twin

Model 52K

The Model 52K was only used on the K/KH and 1957 Sportster. It had an open aluminum housing on the commutator end. A steel cover covered the the opening, and had holes in it where the regulator mounted. The drive gear was affixed with a roll pin. The Model 52K shares many parts with the venerable Model 32E, such as armature, field coils, and aluminum housing.

Model 58

The Model 58 was used across the Harley line, except for the Hummer and Model 165. It had a longer center body than the 52K. The commutator cover was steel, and had an oil cup to allow oiling of the bronze bushing. A spring-loaded band covering the brushes. The regulator mounted on a bracket which was attached to the commutator cover. A chrome-plated outer cover was optional on the XLH.

Model 61

The Model 61 had a roller (needle) bearing instead of a bushing on the commutator end. The End Cover, armature and the bearing are the only differences. The end cover does not have an oil cup.

Model 64

Yes, VIRGINIA, there is a Model 64 generator. The first 12 volt Harley was the 1964 Servi-Car, the only year/model on which the Model 64 generator was used. The Servi went to an alternator in 1965. Sorry, but we know nothing else about these.

Model 65

The Model 65 used a different armature and field coils to produce 12 volts. Otherwise, the Model 65 is nearly identical to the Model 61. This generator was only used for about six months, since there was a problem with sticking brushes - the paper insulator used under the insulated brush holder would swell, causing the brush to stick. A chrome-plated outer cover was optional on the XLH.

Model 65A

The Model 65A solved the problem by rotating the brush plate 180 degrees to put the positive (insulated) brush on the topside to keep it dry. This required swapping the A and F terminals. The Model 65A can be distinguished by the A terminal on the left, looking from the commutator end. A chrome-plated outer cover was optional on the XLH.

Model 65B

The Model 65B was used from 1982 until early 1984. It was made in Japan by Hitachi, and shares no parts with the other generators. Out of scope for our interests, but listing it here provides closure to the generator era.

Drive Gears

A variety of drive gears were used to adapt the generator to the different model bikes, and for differences within the models.

I have noticed that many sellers, particularly on-line sellers, misrepresent the part number / fitment of the gears. It is common to see a 31070-58 gear being sold as 31071-58 and fitting Sportster. The 31070-58 gear does not have an oil slinger, and fits Big Twins. The 31071-58 does have a oil slinger and fits Sportsters. There are many similar looking gears, and this section is intended to help the unwary figure out which gear fits their bike.

Drawing 1
Drawing 2
Part # Dwg Teeth Shaft Style A B C D E F P Notes
K and Sportster
31071-52 1 14 Uses pin 1-1/32 15/16 5/8 7/32 23/64 1-5/8 Yes Used on: 1952-1956 K/KH [ F dim = 1.635]
31071-52A 1 14 Uses pin     ??? ??? Yes Used on: 1957 XL
31071-58 1 14 Threaded 1 11/16 5/8 9/32 5/16 1-19/32 No Used on: 1958-1962 XL, XLH, XLCH
31073-63 2 14 Threaded     5/8 ??? No Used on: 1963-19xx XLH, XLCH
   with 31067-63, ‘Washer, oil separator’
31073-63A 2 14 Threaded     5/8 ??? No Used on: 19xx-up XLH, XLCH
   with 31067-63, ‘Washer, oil separator’
Adapt Model 58, 61, 65, 65A to Other Models
31070-58 2 13 Threaded 31/32 11/16 5/8 1/4 No Used on: Big Twins 1958 - (1969?)
31075-58B 1 14 Threaded         No Used on: 58-64 ServiCar
Similar Looking Gears
31070-30 2 14 Uses pin 1.000   ??? ??? ???   Yes Used on: 1936-1944 OHV
2 14 Uses pin 1.022   ??? ??? ???   Yes Used on: 1945-1957 OHV
31071-37 1 ??? Uses pin 1.000   ??? ??? ???   Yes Used on: 1937-1957 W " G; 1937-1948 74 " 80 Sidevalve

Breather Sealing Items & Recap

Another source of confusion is the items which separate gearcase air from oil to prevent too much oil coming out of the breather tube.

Harley-Davidson added to the confusion. It appears that in earlier years they sold the “25265-52 Bushing, oil separator assembly”, which included the 25270-52 Seal ring, but in later years, these parts were sold separately.

So here is a list of the items from generator to cam cover arranged by years.

Years Generator Gear Washer,
oil separator
Seal Ring Spring Bushing,
oil separator
oil separator
Gear Case
1952-1956 Model 52K 31071-52 25270-52 25287-37 25265-52 25200-52 [1]
1957 Model 52K 31071-52A [2] 25270-52 25287-37 25265-52 25200-57
1958-1960 Model 58 31071-58 25270-52 25287-37 25265-52 25200-57
1961-1962 Model 61 31071-58 25270-52 25287-37 25265-52 25200-57
1963-1964 Model 61 31073-63 [3] 31067-63 25265-63 25200-57
  1. When the -52A gear case cover appeared is unknown. The 1957 parts book shows the -52 for 1952 to 1954. The 1963 book shows -52A.
  2. When the -52A gear appeared is unknown. The 1954 parts book lists the -52. The 1957 book lists the -52A.
  3. There is a -63A gear, but it appears to have appeared later than 1965.