IH: Engine Mechanicals - Sub-01F

Ironhead Transmission Sprocket Cover Pics

Sprocket Cover Part Numbers

All part numbers were gathered from period specific Sportster parts catalogs from 1957-1985 including supplement and updated catalogs.

1952-E1954 K Models34876-52 1)Yes34874-52
Additional notesIt is believed the MoCo made a running change in mid 1954 when they changed worm gears. 2)
The sprocket covers were sold as “complete”.
So the new worm gear should have been installed in a new cover part#.
L1954-1956 K Models34876-52A 3) 4)Yes34874-52Replaced by 34876-52B (1957)
Replaced by 34876-52A (1958)
Used 34876-52A (1959-on)
1957 XL34876-52B 5)Yes Replaced by 34876-57 (1958)
Replaced by 34872-57A (1970) 6)
Additional notesSee Pic section below.
1958-1962 XL/XLH/XLC/XLCH34876-57 7)Yes34874-52AReplaced by 34872-57 (1963)
Replaced by 34872-57A (1970) 8)
1963-1966 XLH/XLCH
and 1967 XLCH
34872-57 9)Yes34874-52AReplaced by 34872-57A
For 1967 XLCH only (1968) 10)
For all models (1970)
1967 XLH34871-67 11)Yes79-67Replaced by 34871-67A (1969)
Replaced by 34871-67B (1970)
1967-1970 XLH34871-67B 12)Yes79-67BOffered in 1971
1968-1969 XLH34869-68 13)Yes79-67A
1968-1969 XLCH34872-57A 14)Yes74-52B
1970 XLH34869-70 15)No79-67B
1970 XLCH34872-70 16)Yes74-52B
1971-1972 XLH34870-71 17)No34879-71Polished.
1971-1972 XLH34871-71 18)Yes34879-71Polished
1971-1972 XLCH34872-71 19)Yes34879-71Polished.
Replaced by 34872-71 (1975)
1973 XLH34870-73 20)No34879-71Black.
Kick cover 34871-71 (offered 1976)
1973 XLCH34872-73 21)Yes Black
1974 XLH34870-71 22)No34879-71Polished.
Kick cover 34871-71 (offered 1976)
1974 XLCH34872-71 23)Yes Polished
1975-1976 XLH34868-75 24)No34879-71AKick cover 34871-71 (offered 1976)
1975-1976 XLCH34896-75 25)Yes34879-71A
1977-1978 XL/XLH34870-75

No34879-75 or
Outer cover

Replaced by 34870-75A (-78A cat)
1977-1978 XLCH34872-75Yes34879-75Outer cover
1977-1978 XL/XLCH34893-75N/A Inner cover
1977-1978 XLCR34885-77No34884-77Outer Cover
1979 XLH34863-79 26)No34879-79AOuter cover
E1979 XLCH34872-79 27)Yes34879-79APolished outer cover
1979 XLS34870-79 28)No34879-79AOuter cover
Replaced by 34869-79 (1990)
1979 XLH/XLCH/XLS34899-79 29)NoNoneInner cover
1980 XLH34911-80 30)No34913-80Polished cover.
Replaced by 34918-81 (1983)
1980 XLS34912-80 31)No34913-80Black cover.
Replaced by 34915-81 (1982)
Replaced by 34915-81A (1984)
E1981-1982 XL34918-81 32)No34917-81Polished cover.
Replaced by 34918-81A (1984)
L1981-1985 XL34911-81 33)No Polished cover.
Replaced by 34918-81A (1985)
E1981 XLS34915-81 34)No Vivid black cover.
Replaced by 34915-81A (1984)
L1981-1982 XLS34912-81 35)No Black cover
1983-1984 XLS34911-81 36)No Polished cover
1983-E1984 XLX34908-83 37)No Aluminum finish cover
L1984-1985 XLX34908-83A 38)No Painted cover

Part #s VS Casting #s

The part number for these sprocket covers DOES NOT APPEAR on the cover.
The casting number is visible on the inside of the covers as well as described in the chart above and the pics below.
The casting number is the same for many covers as that is the base construction of many of them (even though there are still differences between them).
See also HD Part Numbers Explained and HD Casting Numbers, Letters and Symbols Explained in the Sportsterpedia.

Every Ironhead sprocket cover has a casting number, else it's not a factory part.
Likewise, aftermarket covers do not have HD casting numbers.

Clutch Worm Gear

Clutch worm gear (37200-54) was used on 1952-E1954 K Models.
Clutch worm gear (37201-54) was used from L1954-1970 on K Models and Sportsters.

Worm Gear Stop Pin (1970-Earlier Models)

The stop pin (roll pin) is in the cover (underside). Look closely at these as they have a tendency to shear off flush with the cover.
1952-1956 covers do not have a gear stop pin.
1957-1967 covers were drilled through at the roll pin and you could drive it out from the outside. 40)
1968-1970 covers have a boss added to the underside in a wider girth around the worm gear.
The hole for the roll pin is drilled from the underside, through the boss, but not all the way through to the outside of the cover.
This makes removing a broken off roll pin harder.

Grease Fittings

There were 2 types of grease (zerk) fittings used on 1952-1970 sprocket covers.
The threaded fitting is HD part# ( 9851) and it has 5/16“-32 UNEF threads and a straight shank. It only has 1 (maybe 2) useable threads.
A lot of ripped out fittings comes from levering a too tightly fitting gun socket off the nipple (rips the fitting from the thread). 41)
Most gun sockets are adjustable (loosen the business end of the socket from its mate).

You can use an aftermarket grease fitting with longer threads as long as you measure to make sure there is enough room for it. 42)
The fitting below is a Facca (H1631) straight grease fitting that was slightly shortened with a file.
The extra length/thread on the shank doesn't strip out under pressure from your grease gun.

The grease fitting for the starter shaft does not (and should not) thread in far enough to hold the bushing in the bore.
The bushing is pressed in and is held there by tension in the bore and doesn't need to be held in.


Kick Starter Spring Stud

The stud threads into the hole in the sprocket cover to the right of the starter shaft hole.
Hd sold several versions of the stud including parkerized, nickel, zinc and chrome.
The first was parkerized, part# (33088-52) for 1952-1970, then 1971-1978 was zinc, part# (33088-71) and 1979 version was chromed (33088-79).
Replacement parts all years were mixed materials.

44) 45)

The 1971-1979 stud was lengthened from the earlier version. The area between the spring retention groove and hex is longer. 46)


1952-1970 Transmission Sprocket Covers

1957 XL Cover

Cover part# change between 1957 and 1958:
Cover (34876-52B) shows up for the first time in the -57 parts catalog for all 1952-1956 K Models and 1957 XLs.
And the -52A cover was replaced by the -52B cover.
However, the -58 parts supplement catalog labels the -52B cover as “not used, Replaced by 34876-57”.
And for 1952-1956 K Models, cover -52B was replaced by cover -52A, which was already on K models since L1954.
And the -58 catalog also shows the 34876-52A cover as replacement for K Models, not the -52B cover.

1957-1962 XL/XLH/XLC/XLCH Cover

Sprocket Cover part# (34876-57), with kickstarter. The casting number is (34874-52A).
Features and changes:
The angle of the worm gear grease (zerk) fitting changed to (angled forward 1:00) as opposed to the vertical position on the K Model covers.
The grease fitting is threaded into the boss.
Also the grease (zerk) fitting position for the kick starter crankshaft was moved to the (9:00) position.
A boss is cast into the cover at the (9:00) position as extra strength for the grease fitting which is pressed in.
The pin stop for the worm gear is simply pressed into a hole drilled through the cover at an angle.
The center cavity under the bar on the cam cover side resembles the back side of an arrow.

Pics of used covers. Click on any pic to enlarge:
48) 49)

50) 51)

1963-1966 XLH/XLCH, 1967 XLCH

Sprocket Cover part# (34872-57), with kickstarter. The casting number is (34874-52A).
Features and changes:
The grease (zerk) fitting position for the kick starter crankshaft was moved to the forward side of the bushing hole (1:00).
A long angled boss was added off the crankshaft bushing bore for the new grease fitting location.
The 1962-previous boss is still present at the (9:00) position but it is not drilled out for a fitting.
The pin stop for the worm gear is pressed into a hole drilled through the cover at an angle.
The center cavity under the bar on the cam cover side resembles the back side of an arrow.

52) 53) 54)

1967 XLH Cover

Sprocket cover part# (34871-67), with kickstarter.
The 1967 XLH cover has a new cover casting and still has the single rib but it's modded for electric start motor. 55) 56)
It's a 1 year, 1 model only, cover (machined for both kick and electric start as fitted from factory).

1968-1969 XLH Cover

The original 1968-1969 XLH cover is HD part# (34869-68), with the upper dowel in the rear of the cover attaching bolt and machined for an optional factory kick start kit. 57)
The ribbed design matching the cam cover was removed for a smooth surface across the cover instead (often referred to as a moonpie cover).
The worm gear roll pin bore does not go all the way through to the front of the cover.

1968-1969 XLH models not using the kick starter, a metal plug and a hex head bolt were available to plug the starter shaft hole and kicker spring stud on the sprocket cover.
Plug (56238-62) has thin metal “fingers” that hold it into the starter shaft hole. And the spring stud replacement is a 3/8”-16 x 1/2“ hex head bolt (3440).

58) 59)

Below are pics of a used 68-69 cover. Click on a pic to enlarge.
60) 61) 62)

1968-1969 XLCH Cover

1968-1969 XLCH also had a new smooth cover casting (moonpie cover) with the upper dowel pin location in the front of the cover attaching bolt. 63)
Sprocket cover part number (34872-57A), with kick starter. Casting number (74-52B).

64) 65)

1967-1970 XLH (replacement) Cover

Sprocket Cover (34871-67B), with kickstarter. This cover was sold in 1971 as a replacement for 1967-1970 XLH models.
Click on a pic to enlarge 66)

1970 XLH Cover

1970 XLH sprocket Cover is part# (34869-70) (moonpie cover).
It has an upper dowel pin hole in the rear of the upper cover attachment bolt and is not machined for a kick start kit.
(the kicker kit machining delete may have been a running change)

Click on a pic to enlarge
67) 68)

Additional pics

69) 70)

1970 XLCH Cover

There were two versions of the 1970 XLCH style kicker cover (both moonpie covers). 71)
First one was factory fitment on some/all 1970 XLCH. It has 1 upper dowel pin hole in the rear of the upper cover attachment bolt.
The second version is machined for 2 upper dowel pin holes, 1 in front and 1 in the rear of the cover attachment bolt;
Rear dowel location is for use with kick only using electric start cases and dry clutch. (ie 70 XLCH).
Front dowel location is for use with earlier kickstart only cases.
This is the cover that's fitted to the XR750 and supplied by the Parts Department as replacement to single rib casting after it was dropped.
If these two versions were different part numbers, is possible.
Sprocket cover part number (34872-70), with kick starter. Casting number (74-52B).
The pic below shows the different location of the upper dowel between the 1969 and 1970 XLCH covers.

This is the first version, uses the same 74-52B casting as the 68-69 version. 73)
74) 75)

1971-1976 Transmission Sprocket Covers

A service replacement mainshaft sprocket nut (35049-71) was developed to prevent transmission oil leakage from the sprocket splines on 1971-E1984 models.
Per Service Bulletin M-886, the inner and outer sprocket covers on some models needed to be modified to use the new sprocket nut.
Click Here to download the service bulletin PDF.
To use this nut on 1981-E 1984 models, it's necessary to remove a portion of the cover to prevent interference between the nut and the cover.
So you may find some used factory covers that appear to have been hogged out for this purpose.
On 1977-1978 models with inner sprocket cover (34893-75), it is necessary to open up the 0.88” opening in the cover to 1.75“.
On 1979 models with inner cover (34899-79), a 1.75” diameter hole must be located and drilled as shown in the service bulletin.

The new sprocket nut encloses the end of the mainshaft and provides a metal to metal seal between the sprocket, lockwasher and nut when tightened to 35-65 ft-lbs.


1971-1972 XLH, 1974 XLH Cover

Sprocket Cover (34870-71), polished, without kick starter.
Click on a pic to enlarge 77)

1973 XLH Cover

Sprocket Cover (34870-73), black, without kick starter.
Click on a pic to enlarge 78)

1971-1976 XLH Optional Kicker Cover

This cover was offered in the -71 and -72 parts catalogs but not again until the 1967 catalog for 1971-* (1976).
The -78A parts catalog lists this cover for 1971-1974 XLH models. However it will bolt on to 1971-1976 XLH models.
Sprocket cover part# (34871-71), polished, with kicker starter. Casting number is (34879-71).
It has the half moon cutout around the starter, the kicker shaft hole/bushing and the kicker spring stud.
Click on a pic to enlarge

79) 80)

1971-1972 XLCH, 1974 XLCH Cover

Sprocket cover part number (34872-71), polished, with kick start. Casting number (34879-71).
Click on a pic to enlarge

81) 82)

1975-1976 XLCH Cover

Sprocket cover part# (34896-75), polished, with kick starter. Casting number is (34879-71A).
Click on a pic to enlarge: 83)

1975-1976 XLH Cover

Sprocket cover part# (34868-75), polished, without kick starter. Casting number is (34879-71A).
Click on a pic to enlarge: 84)

1975-1976 sprocket cover (34868-75). 85), 86)

1977-1978 Transmission Sprocket Covers

The 1977-1978 XLCH cover is recognizable from a couple of things. Most obvious is the small 1/4“ hole located about 1” or less above the kicker shaft bushing hole. 87)
This is the mounting stud for the extra support bracket, which is a must have on 1977-1978 XLCH with a kicker if you dont want to crack the poorly mounted sprocket cover.
The other thing on the 1977-1978 cover is the half-inch hole for the footpeg mount at the bottom front of the cover, with small 1/8“ dowel locating holes.
Also the location of the two main cover mounting bolts is different from the earlier models.
Earlier models had two big honking 5/16” or 3/8“ hex-head mounting bolts, one top and one bottom of the cover.
The 1977-1978 cover relies on the big half-inch footpeg mounting stud and a couple of crappy little 1/4” phillips head screws.
Hence the problems if you don't fit the extra support bracket to the rear engine mounts.

From the -78A parts catalog, a Sprocket Cover Kit (34850-77) was available to reinforce the XLCH cover.
It consists of;
Updated cover (no part#).
A 1/4“-20 x 5/8” screw (1789)
And (2) 3/8“-24 x 9/16” x 3/8“ hex locknuts (7506).
From the -78B parts catalog, the part#s in that same kit changed somewhat.
Cover (still no part#).
A screw (1305) which was originally a 1/4”-20 x 1“ Pozidriv Fillister Head Screw.
(2) 3/8”-24 x 9/16“ x 3/8” hex locknuts (7506). Plus Spacer Assembly (34848-77). The spacer is actually a brace that bolts to the rear motor mount using the 2 locknuts.
The kicker shaft slides thru the brace (or spacer, or extra support bracket as mentioned above) which bolts to the cover using the 1/4“ hole above the kicker shaft.
Click Here to reference Hopper's 1977-1978 Kicker Cover Damage Repair article in the Sportsterpedia. The support bracket is pictured there.
The support tube itself does not actually touch the kicker shaft, so gives no support on it's own.
And you can't put a bushing inside that tube to support the kicker shaft because of the way the shaft is stepped down in diameter inboard of the sprocket cover.

It's interesting that the 1977 cover has a -75 part number. Even more interesting that the -75 casting number has a light number “7” ghosting through the ending number “5”.
Most all 1977-1978 covers found have this same condition in varying degrees.
However, the only cover found with an actual -77 casting number is the XLCR sprocket cover (which has the upper rear “winged” look on 1979 models.

Inner Sprocket Cover
The 1977 and 1978 years were unique in that there is another stamped steel inner cover (34893-75) under the aluminum sprocket cover. 88)
The steel piece holds the rear brake cable and light switch.
Fortunately, HD made this cover just large enough to fit around a 23T sprocket, otherwise we'd be in for some serious modification work.

1977-1978 XL/XLH Outer Cover

Click Here to view Hopper's 1977-1978 sprocket cover repair article in the Sportsterpedia.

The original 1977 XL/XLH Outer Sprocket Cover part# is (34870-75), polished, without kick starter and the casting number is (34879-75).
Both the early 1977 and late 1977-1978 XLH covers have the single web on the back side for strength.

Somewhere in the mid-late 1977 season, a change was made to the original cover and the casting number changed with it to (34876-75).
However, the part number stayed the same. The lower dowel hole was drilled through and the front of the cover milled for 1/4”x20 screw.

Click on any pic below to enlarge:

Early 1977 version:
89) 90)

Late 1977-1978 version.
91) 92)

Replacement Outer Sprocket Cover (34870-75A) for 1977-1978 XL-XLH, polished, without kick starter.
This version added extra webbing on the rear for more strength and the casting number was updated to (34876-75A).

93) 94)

More information on additional lower cover screw:
L1977-1978 models and also some later models have a 1/4“-20 threaded hole that goes through the lower rear dowel and into the cast boss on the side of the transmission.
A 1/4”-20 x 1-3/4“ posi-drive head screw (1308) was used thru the lower (hollow) dowel for extra clamp support on the sprocket cover.
The L77 cover has an extra hole in the location for the screw although most folks swap the posi-drive screw to a phillips head screw.
HD most likely added the fastener to help support an inherently weak cover when using the OEM folding kicker required by the big 2-1 muffler. 95)
This threaded hole may or may not go all the into the transmission case.
If it does, you may need to add some thread sealer on the screw threads before installing it, or there will be some oil spillage there.
The pics below detail the hole locations in the case and the cover. 96)

1977-1978 XL/XLCH Inner Sprocket Cover

1977-1978 Sportsters models (except XLCR) have a thin steel inner sprocket cover that has mounting tabs for the rear brake light switch and brake cable.
It helps to hold the sprocket cover in place and also protects oil lines from the chain sprocket. 97)
Another possible big advantage of the inner cover is that, in the event of a broken chain, the inner cover should help prevent the chain from jamming against the case and causing extensive damage. The loose chain would likely remain on the sprocket due to the close-fitting steel cover until it ran all the way through. 98)
Cover part number is (34893-75), made from about 1/8” stamped steel.

You may have to fiddle a bit to get the outer sprocket cover to fit over the inner steel cover. 99)
Seems that the brake cable tends to cock the inner cover and it can pop off the dowels causing the outer cover to not seat.
It helps to get down on the floor and look up under the outer cover to make sure the dowels protrude through the inner cover before tightening down the screws.
It may help keep from cracking the aluminum cover.
Also, if you use aftermarket outside covers, you may find the footpeg stud hole is not centered and causes some misalignment.
You may need to hog out the hole oversize to get a proper cover fit.
It's also common for the inner sprocket cover to have an impression of the shaft and nut worn into it. You can do a little gentle hammering on it to flatten it out. 100)
The used inner cover below has that same impression.

101) 102)

Below is how it looks inside the outer cover and “dressed” with the brake light and cable mounted.
The top sprocket cover bracket below isn't factory but a homemade special that the original bike never had. 103)
Basically it is a piece of 1-1/2“ inch steel angle cut and drilled to fit to 2 bolt holes on top of the tranny where the E start battery box normally mounts.
Then a small piece welded on the end so it snugs up against the cover behind the existing top mount hole in the cover.
Drill through the cover into the angle, then tap for a 5/16” bolt and drill the cover to clear the 5/16“ bolt.

104) 105)

1979 XLH

Outer Sprocket Cover(34863-79), polished, without kickstarter.
Click on a pic to enlarge: 106)

1979 XLCH Cover

Outer Sprocket Cover (34872-79), polished, with kichstarter.
The master cylinder was mounted high on the 79's to miss the optional kickstarter shaft. Later models have no kicker.
Click on a pic to enlarge: 107)

1979 XLS Cover

Original Outer Sprocket Cover(34870-79), factory painted silver, without kickstarter.
Click on a pic to enlarge: 108)

1979 XLH-XLCH-XLS Inner Sprocket Cover

An Inner Sprocket Cover (34899-79) was used for all 1979 model Sportsters. The pics below are of a used inner cover.

109) 110)

Here is how the inner cover fits in the outer cover.
Also shown is how the rear brake linkage is connected over the cover with the return spring attached to the cover.
111) 112)

1980 XLH Cover

Sprocket cover part number (34911-80), polished. Casting number (34913-80).
The mounting holes for the rear master cylinder are now machined lower on the cover.

113) 114)

1980 XLS Cover

Original sprocket cover part number (34912-80). Casting number (34913-80).
Same cover as the 1980 XLH except it's painted black.

This is the original cover.

116) 117)

1953 K Model Spare Parts Catalog
Harley K Model site
1954 K Model Spare Parts Catalog
1957 HD Sportster and K Model Parts Catalog
1958 HD Sportster and K Model Parts Catalog Supplement
6) , 8) , 15) , 16)
1970 HD Sportster and K Model Parts Catalog
1958-1963 HD Sportster and K Model Parts Catalogs and Supplements
9) , 11)
1967 HD Sportster and K Model Parts Catalog
10) , 13) , 14)
1968 HD Sportster and K Model Parts Catalog Supplement
12) , 17) , 18) , 19)
1971 HD Sportster and K Model Parts Catalog
20) , 21)
1973 HD Sportster Parts Catalog Supplement
22) , 23) , 24) , 25)
1975 HD Sportster Parts Catalog Supplement
26) , 27) , 29)
1979 HD Sportster Parts Catalog
28) , 30) , 31)
1980 HD Sportster Parts Catalog
1981 HD Sportster Parts Catalog
1981, 1982, 1983, 1984, 1985 HD Sportster Parts Catalogs
1981, 1985 HD Sportster Parts Catalogs
1981, 1982 HD Sportster Parts Catalogs
1983,1984 Sportster Parts Catalogs
1984, 1985 Sportster Parts Catalogs
1985 Sportster Parts Catalog
39) , 48) , 49) , 50)
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