IH: Electrical System



The Keyswitch is fed from the main Circuit Breaker. Typically, this feed wire is RED. The Keyswitch has two positions (besides OFF).

There is a RUN position & a LIGHTS position. This allows the lights to be off for starting (especially kick starting) but then can be turned on by moving the keyswitch to the second on position. But sometime in the late 70's, the MoCo began putting a shorting wire across both output connections of the Keyswitch. This meant that all the circuits are powered whenever the Keyswitch is ON, so that the lights are guaranteed to be on (basically making the keyswitch simply an ON/OFF switch). The Keyswitch labels were likely to be B - IG - L for Battery, Ignition & Lights.

Brake Switch

Front and Rear Brake Switches
Year ModelPositionSwitch Part#AdditionalYear ModelPositionSwitch Part#Additional
1959-1966Rear72004-52Complete1973-1981Front72001-69BSwitch only
1967-1972Rear72004-67Kit with wires1977-1978Rear
L1969-1972Front71900-70Includes terminal1979-1985Rear72023-51ASwitch only
1973-1974Rear72004-70Switch only1982-1985Front71574-82Includes terminal
and wiring
1975-1976Rear72004-75Switch only

The stock 77 rear brake light switch is a cheesy little thing that attaches to the pressed metal inner sprocket cover/brake cable mounting plate under the aluminum sprocket cover. 1) They are tiny and often get clogged up with chain gunk in there. The little flat plate sticking out from the end of the cable operates it. It mounts on a right angle metal bracket going to the quarter nut and stud above, allowing adjusment.

Rear Brake Switch (72001-69B) on 1977 XLCH.


Sub Documents


All Ironhead Sportster speedos, whether tranny driven or front wheel driven, are 2:1 ratio.
1957-72 - Transmission Driven - 2:1 Ratio Speedometers
1973-83 - 19“ Wheel Driven Right Side - 2:1 Ratio Speedometers 3)
1984-85 - 19” Wheel Driven Left Side - 2:1 Ratio Speedometers
. Driven Unit = 67127-84A for use with 2:1 Speedometers - (CableRPM-2000=60mphOnSpeedo)

MPH Speedometers KPH Speedometers
Part#Year ModelNotesPart#Year ModelNotes
67007-521952-1954 K Models120 MPH67008-521952-1956 K Models
1957-1958 Sportsters
(except XLC/XLCH)
1955-1956 KH
1957-1958 Sportster
(except XLC/XLCH)
120 MPH67008-521952-1956 K Models
1957-1958 Sportsters
(except XLC/XLCH)
67007-591959-1964 Sportsters120 MPH67008-591959-1967 Sportsters
(except XLCH initially)
67007-59A1965-E1967 Sportsters120 MPH67008-59A1959-1968 SportstersKPH.
New part# in 1968 retrofit
67007-59BL1967-E1969 Sportsters150 MPH67008-59B1959-1969 SportstersKPH
67007-59CL1969 Sportsters150 MPH67008-701970 SportstersKPH
67007-701970 Sportsters150 MPH67021-701970-1972 SportstersKPH
67020-701970-1972 Sportsters150 MPH67021-731973 SportstersKPH
67020-731973 Sportsters150 MPH67021-73A1973 SportstersKPH
update in 1976
67020-741974 Sportsters150 MPH67043-741974 SportstersKPH
67020-74A1975-1976 Sportsters150 MPH
update retros to 1974
67043-74A1975-1976 SportstersKPH
update retros to 1974
67020-74B1977-1979 Sportsters150 MPH
update retros to 1974
67043-74B1977-1979 SportstersKPH
update retros to 1974
67007-791979 XLSMPH67043-75B1980-1981 XL
1981 XLS
67007-79A1980 XLSMPH, w/ bracket
replaced 670079 in 1980
67043-75C1982-1983 XL
1982 XLS
supercedes 67043-75B
67020-75D1980-1983 XL
1981-1982 XLS
85 MPH67008-791979 XLSKPH, w/ bracket
67016-831983 XLS
1983-1984 XLX
85 MPH, complete67008-79A1980 XLSKPH
67037-83E1984 XLMPH, w/ wiring67010-831983 XLS
1983-1985 XLX
KPH, complete
67061-831984 XLSMPH, w/wiring67062-83L1983-1985 XLX
1984-1985 XLS
KPH, w/wiring
67100-831983-1984 XLSMPH, complete67101-831983-1985 XLSKPH, complete
67016-851985 XLXMPH, complete
67037-851985 XLMPH, w/ wiring
67061-851985 XLS/XLXMPH, w/wiring
67100-851985 XLSMPH, complete
67037-85AL1984-1985 XL
1985 XLS/XLX
120 MPH, w/ wiring

Speedometer Drive Gear (1952-1972)

The mechanical speedometer on K Models / XLH from 1952-1972 and XLCH from 1959-1972 is run by a (11T) gear unit attached to the transmission.
This was not used on 1958 XLC or XLCH.
4) 5)

The speedometer drive unit goes into the hole in the lower right side of the transmission beside the oil pump.
The pic on the right shows the drive unit as installed from the inside.
6) 7) 8)

Staring down a problem with the speedometer not working can be catastrophic when visualizing the possible causes and particularly the effects thereof.
Also, if you're not going to use the OEM speedo drive, then remove it and plug the hole. That freewheeling drive has been known to destroy the trans and engine case. 9)
Just unscrew it and screw in a plug. Colony makes a Speedometer Drive Block-Off Plug (2057-2) for K Models and XLs.

This..Yields that….This particular incident luckily didn't hurt any engine parts
Broken teeth on bent speedo drive unit 10)Metal pieces in case behind trap door 11)Busted teeth on tranny 12)

Speedometer Drive Gear (1973)

The speedometer drive unit was moved to the front wheel, right side, in 1973. 1970-1973 XLH, XLCH used Veglia (Italian made) instruments.
And the 73 drive unit (67127-73) was also from Veglia. In 1974, the MoCo started using Nippon Seiki (Japan) gauges and drive units.
The new drive unit didn't have the grease fitting as did the 73 unit but has the same part number as in 73, and retrofitting to 73 models for replacement.

13) 14) 15)

Speedometer Hole Plug (1958-1972 XLCH)

There is a 11/16“x20 hex head hole plug (24575-52) for 1958-1972 XLCH's not running a speedometer.
It gets installed in place of the speedometer drive gear unit in the lower rear of the right case.


The first mention of a tach used on a Sportster is the L1962 XLCH per the -63 parts catalog.
Several tach kits were sold in 1965 for current and prior model XLH models per the -66 parts catalog supplement.

Year Model Tach Notes
L1962- XLCH92051-62Part of Tach Kit (92050-62) mounted on handlebars. (Smith)
1962-1964 XLCH92051-65Part of Tach Conversion Kit (92050-62A), replaces (92051-62)
1965-1966 XLCH92051-65Part of Tach Kit (92058-59) mounts speedometer and tach to forks on 1959-1965 XLCH
1967-1969 XLCH92051-65Part of Tach Kit (92057-67)
1957-1964 XLH92051-65Part of retro Tach Kit (92049-57) in 1963
E1965 XLH92051-62Part of Tach Kit (92049-65)
92051-62AReplaced 92051-62 with Tach Kit (92050-62A)
L1965-1966 XLH92051-65Part of Tach Kit (92049-65A)
1967-1969 XLH92051-65Part of Tach Kit (92048-67)
1970 XLH/XLCH92059-70Part of Tach Kit (92048-70). Made by Veglia (Italy)
1971-1973 XLH/XLCH92051-70Part of Tach Kit (92048-71) Made by Veglia (Italy)
1974 XLH/XLCH92051-74Made by Nippon Seiki (Japan)
1975-1976 XLH/XLCH92051-74ARetro to 1974. Made by Nippon Seiki (Japan)
1977-1979 XLH/XLCH92051-74BRetro to 1974. Replaced by 92051-75D. Made by Nippon Seiki (Japan)
1979 XLS92053-79With bracket. Replaced by 92053-79A. Made by Nippon Seiki (Japan)
1980 XL92051-75DWith bracket. Made by Nippon Seiki (Japan)
1980 XLS92053-79AWith bracket. Supersedes 92053-79. Made by Nippon Seiki (Japan)
1981-1982 XL/XLS92051-81Electronic. Replaced by 92051-81A. Made by Nippon Seiki (Japan)
1983 XL92051-81AElectronic. Replaced 92051-81. Made by Nippon Seiki (Japan)
1983-1984 XLS92060-83Electronic, complete w/ bracket
1983 XLS92059-83Electronic, w / bulb and socket
1983 XLS92060-83Electronic, complete
E1984 XL67111-83Speedometer and Elect Tach Kit (67099-84)
L1984-1985 XL67111-85Speedometer and Elect Tach Kit (67099-85)
1985 XLS92059-85Electronic, w / bulb and socket
1985 XLS92060-85Electronic, complete w/ bracket

Tach Drive Gear (1971-1980)

The tach drive gear unit (92097-71) for 71-80 models screws into the cam cover between #3 and #4 cams.
A worm type gear is pressed onto #4 cam that drives the tach drive gear unit. Both gears on the cam and tach drive have 11 teeth.
So there is a 1:1 ratio between these two gears.
However, the cam turns 1 revolution per every 2 TDC revolutions of the front piston leaving a 2:1 ratio at the tachometer head.
The drive unit gets a washer gasket (67142-52) on top for the threaded coupler on the cable connecting the drive unit to the tach head.

17) 18)

19) 20) 21)

Tach Hole Plug

If you are not using the tach, you can remove the drive unit and plug the hole.

L1962-1969 XLCH tach plug (92077-62) is used to plug the hole at the magneto.
The plug is pushed into the hole and it has an O-ring (11110) on the end.

1971-E1984 Sportsters can use the Colony plug below to plug the hole in the cam cover.
Just unscrew the drive and screw in the plug (with seal washer).
22) 23)

24) 25)

Misc Gauges

HD Head Temperature Gauges

Head Temp Gauge (75002-69) became available through the -70 Sportster parts catalog (among other models) as part of Kit# (75000-69) and also sold by itself.
Made for +12V systems from 1965-1976.
The gauge signal comes from a sending unit (75005-69) attached to the front head with a thin nut (7692) and wired with a cable assembly (75003-69).
The gauge sits inside a handlebar mounted bullet style housing (74479-68) with a bezel (74472-68).
The assembly mounts to the handlebar with mounting bracket (74484-68) and handlebar clamp (45030-65A).

Head Temp Gauge (75002-77) was for use on 1977-1981 Sportsters. It has an illuminated face and measures temps 200-500F (95-260C).
Per IronMick, to install the sending unit for the gauge, you drill a hole in the top fin of the front cylinder head (left side). 26)
Then insert the threaded part of the sender into the hole. The special nut is thin enough to fit between the two fins.

27) 28)

Volt Meter

1977-1978 XLH, XLCH got a volt meter (74432-77). The part number was updated in the -78B parts catalog to (74432-77A).
It has a black face, is app. 2” in diameter, 2.3“ wide bezel, 2” long and reads +10 to +16 volts.

29) 30) 31)



In Late 1977, Shorter Headlight Bracket Mounting Bolts Used

  • In late 1977, shorter bolts were used to mount the headlight bracket to allow it to be installed or removed with the handlebars clamped in place. The shorter bolt also allows for the mounting of the headlight bracket after mounting the speedometer / tachometer bracket underneath the handlebar upper clamp which provides easy access to the wiring connections at the headlight terminal block.
  • The shorter bolts 5/16“x18 1-1/8” (43868-72) replaced the longer 5/16“x18 1-1/4” bolts (2871W). The longer bolts can also be shortened for this application. 32)

Tail Light - License Light

Turn Signals

(1973-85 Simple Turn Signal Function)
These model years HD implemented a basic turn signal circuit using a bi-metallic, current/heat-controlled, Turn Signal Flasher Unit similar to those in automobiles. The 12v power wire feeds thru the Flasher and then goes to the handlebar switches. The Left or Right handlebar turn signal switch could be pressed to feed the power to the bulbs on that side of the bike. When connected to the bulbs, thus completing the circuit, the Flasher unit would supply power until the current flowing through it would heat the bi-metallic elements sufficiently to cause a break (like a circuit breaker) in the circuit. Once the flasher cooled down, the bi-metallic elements would again conduct power to the turn signal bulbs, thus causing an on-off cycle that repeated until the handlebar switch was released.

From 1973-1981, the handlebar TS switches were small pushbuttons. They were momentary contact. The turn signal only stayed flashing while the button was depressed.
From 1982-1985, the handlebar TS housings were changed, creating a larger TS button. The switches were still momentary contact, working only while the button was depressed.

  • (Converting to LEDs) - Because of the way these bikes were wired, you can replace the single current/heat-activated flasher with a new electronic flasher that is capable of properly flashing LEDs or Incandescent bulbs. However, the indicator light may need to be modified by grounding one side and feeding power from the right and left circuits thru diodes to the power side of the indicator.

Signal-STAT Flashers (6v)

From a service bulletin in 1961:
Different flasher modules have different characteristics. It is important to use the appropriate one when replacing them. For instance:

  • Flasher (68543-61) was originally used for directional signals with 21 candlepower to the front and rear lamps (6872-50) and 1 candlepower pilot lamps (71090-47). If any of the signal bulbs burn out, the pilot lamp in the same circuit will remain on.33) Flasher (68543-61A) was the replacement for directional signals. 34)
  • Flasher (68542-61) is used for pursuit lamps or other flashing lamps which use either one or two 32 candlepower lamps (68715-49).35)
Year modelPart #Used ForMarkingsApplication
1957-E196368543-61Directional signalsN 221-6V63-prongs: X (hot), L (switched), P (not used)
1957-196568543-61ADirectional signals143-12V6Replaced 68543-61 in L1963.
Disregard the 12V markings per HD.
2 prongs: X (hot), L (switched)
68542-61Pursuit lampsF 421-6V6

Hazard Warning Flashers

1968 and 1969 XLH got a Flasher Kit (68541-68). 1970-1972 XLH/XLCH got Flasher Kit (68540-70). 1973-1975 XLH/XLCH got Flasher Kit (68540-73).

Hazard Flasher Kit (68540-70)……… Click Here to download the instruction sheet.
36) 37) 38)


There was a truck load of changes in the horn mounts between late 1970 till 1975. 39) The changes weren't really cataloged in the part books.
1965-1970 all used the same geometry. 1965 and 1966 used different stuff than 67> but the end result was same.
And this 1st gen stuff was used on some 1971's, maybe even some 72's also. This set up used the larger diameter, short, stiff, 5/16“ stud rubber mount.
It held the horn way more solid than the later smaller, longer, 1/4” stud rubber mount. Both 1st gen brackets had less inward offset than any of the later ones.
The shananigans began in late 1970 with the intro of the 'low' seat kit.
1971 and maybe the 1972 bikes that came from the factory using the older standard seats supposedly came with the 1st gen 65-70 setup.
In late 1971, the low seat was available factory installed for the 1st time.
The low seat required the ignition switch to be moved from the right side under the high seat to the left side on top motor mount where it fouled the horn brackets.
At first, the new brackets with deeper offsets that opened up room for switch were supplied that used the old 5/16“ rubber.
There were some issues with interference. The smaller rubber mount and another set of new brackets were furnished to solve that issue.
But the 1/4” rubber mount let the horn flop around to much hitting fins and/or shaking the wire loose from the slip-on terminal.
The bumper was the fix for this. This 3rd gen setup was used till 1974. In 1975, a bigger ignition switch was used. New brackets again, 4th gen.
There are so many different brackets used that having mismatched stuff is common changing horn position to who knows where.

Below is a rebuild of the stock Delco Remy horn from a 68 XLCH. 40)
There are horn rebuild kits available, but they are pretty simple in design and a good cleaning may be all that is needed.
The repop one from J&P Cycles is on the right (3rd pic below). It has 2 wire connections as opposed to the single wire connection on the original horn.

41) 42) 43)

A bench grinder was used to grind the rivet faces off flat. You can also use a drill bit that is larger than the hole in the rivets to drill off the face.
Then you can use a center punch to knock the rivets out or pull them out of the other side with pliers.
Then separate the halves and clean up all surfaces with sand paper or a wire wheel.

44) 45) 46)

You can check the continuity of the coil but be careful not to break the wire.
Use some 400 grit sand paper to lightly resurface the contact points (you may have to push the lower contact down to get the sandpaper in and out).
After everything is cleaned up, reassemble the horn and test.
There is a small screw on the back of the horn, you can make slight turns on it to adjust the horn for the best sound.
Keep in mind that too far one way or the other and the horn will not work at all. Use pop rivets to put the horn back together after a thin coat of RTV.
Ensure that you don't get any sealant on the vibrating plate or it will not work.

47) 48) 49)

4) , 5)
photo courtesy of Ebay seller, American Vintage Cycles. Link to Ebay Store
6) , 7)
68 XLCH speedometer drive gear location, photo by a0gambo of the XLFORUM http://xlforum.net/forums/showthread.php?t=1682985
Inside view of a 69 XLH speedo drive gear, photo by austinshovel of the XLFORUM http://xlforum.net/forums/showthread.php?t=1940385
13) , 14) , 15)
photo courtesy of Ebay seller, Evil Genius M/C Parts. Link to Ebay Store
photo courtesy of Ebay seller, 57harleyrider. Link to Ebay Store
17) , 18)
photo courtesy of Boneyard Cycles in Melbourne, FL, Link to Ebay Store
27) , 28)
photo courtesy of Hyatt's Recycled Cycles. Link to Ebay Store
29) , 30) , 31)
photo courtesy of Boneyard Cycles in Melbourne, FL. Link to Ebay Store
HD Service Latter ML-38 dated March 4, 1977
33) , 35)
HD Service Bulletin #438 dated March 28, 1961 pg OC-59
HD Service Bulletin #473 dated February 28, 1963 pg OC-97
36) , 37) , 38)
photo courtesy of Ebay seller, jrs vintage harley parts. Link to Ebay Store
42) , 44) , 45) , 46) , 47) , 48) , 49)
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