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

Year Model	Part Number	For Kickstart?	Casting Number	Notes
1952-E1954 K Models	34876-52 1)	Yes	34874-52
Additional notes	It 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 Models	34876-52A 3) 4)	Yes	34874-52	Replaced by 34876-52B (1957) Replaced by 34876-52A (1958) Used 34876-52A (1959-on)
1957 XL	34876-52B 5)	Yes		Replaced by 34876-57 (1958) Replaced by 34872-57A (1970) 6)
Additional notes	See Pic section below.
1958-1962 XL/XLH/XLC/XLCH	34876-57 7)	Yes	34874-52A	Replaced by 34872-57 (1963) Replaced by 34872-57A (1970) 8)
1963-1966 XLH/XLCH and 1967 XLCH	34872-57 9)	Yes	34874-52A	Replaced by 34872-57A For 1967 XLCH only (1968) 10) For all models (1970)
1967 XLH	34871-67 11)	Yes	79-67	Replaced by 34871-67A (1969) Replaced by 34871-67B (1970)
1967-1970 XLH	34871-67B 12)	Yes	79-67B	Offered in 1971
1968-1969 XLH	34869-68 13)	Yes	79-67A
1968-1969 XLCH	34872-57A 14)	Yes	74-52B
1970 XLH	34869-70 15)	No	79-67B
1970 XLCH	34872-70 16)	Yes	74-52B
1971-1972 XLH	34870-71 17)	No	34879-71	Polished.
1971-1972 XLH	34871-71 18)	Yes	34879-71	Polished
1971-1972 XLCH	34872-71 19)	Yes	34879-71	Polished. Replaced by 34872-71 (1975)
1973 XLH	34870-73 20)	No	34879-71	Black. Kick cover 34871-71 (offered 1976)
1973 XLCH	34872-73 21)	Yes		Black
1974 XLH	34870-71 22)	No	34879-71	Polished. Kick cover 34871-71 (offered 1976)
1974 XLCH	34872-71 23)	Yes		Polished
1975-1976 XLH	34868-75 24)	No	34879-71A	Kick cover 34871-71 (offered 1976)
1975-1976 XLCH	34896-75 25)	Yes	34879-71
1977-1978 XL/XLH	34870-75 34870-75A	No	34879-75 or 34876-75 34876-75A	Outer cover Replaced by 34870-75A (-78A cat)
1977-1978 XLCH	34872-75	Yes	34879-75	Outer cover
1977-1978 XL/XLCH	34893-75	N/A		Inner cover
1979 XLH	34863-79 26)	No	34879-79A	Outer cover
E1979 XLCH	34872-79 27)	Yes	34879-79A	Polished outer cover
1979 XLS	34870-79 28)	No	34879-79A	Outer cover
1979 XLH/XLCH/XLS	34899-79 29)	No	None	Inner cover
1980 XLH	34911-80 30)	No	34913-80	Polished cover. Replaced by 34918-81 (1983)
1980 XLS	34912-80 31)	No	34913-80	Black cover. Replaced by 34915-81 (1982) Replaced by 34915-81A (1984)
E1981-1982 XL	34918-81 32)	No	34917-81	Polished cover. Replaced by 34918-81A (1984)
L1981-1985 XL	34911-81 33)	No		Polished cover. Replaced by 34918-81A (1985)
E1981 XLS	34915-81 34)	No		Vivid black cover. Replaced by 34915-81A (1985)
L1981-1982 XLS	34912-81 35)	No		Black cover
1983-1984 XLS	34911-81 36)	No		Polished cover
1983-E1984 XLX	34908-83 37)	No		Aluminum finish cover
L1984-1985 XLX	34908-83A 38)	No		Painted cover

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 (37200-54) was used on 1952-E1954 K Models.
Clutch worm gear (37201-54) was used from L1954-1970 on K Models and Sportsters.
³⁹⁾

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.

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.

⁴³⁾

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⁾

⁴⁷⁾

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.

⁴⁸⁾

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.

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:
^{49) 50)}

^{51) 52)}

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.

^{53) 54) 55)}

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. ^{56) 57)}
It's a 1 year, 1 model only, cover (machined for both kick and electric start as fitted from factory).

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. ⁵⁸⁾
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).

^{59) 60)}

Below are pics of a used 68-69 cover. Click on a pic to enlarge.
^{61) 62) 63)}

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. ⁶⁴⁾

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
^{65) 66)}

Additional pics

^{67) 68)}

There were two versions of the 1970 XLCH style kicker cover (both moonpie covers). ⁶⁹⁾
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 (34871-67B), with kickstarter. This cover was sold in 1971 as a replacement for 1967-1970 XLH models.
Click on a pic to enlarge ⁷⁰⁾

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

Sprocket Cover (34870-73), black, without kick starter.
Click on a pic to enlarge ⁷²⁾

Sprocket Cover part# (34868-75), polished, without kick starter. Casting number is (34879-71A).
Click on a pic to enlarge: ⁷³⁾

1975-1976 sprocket cover (34868-75). 74), 75)

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).
It's interesting that the 77 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 77-78 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.
And the XLCR cover has the upper rear “winged” look that was adapted in 1979.
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:
^{76) 77)}

Late 1977-1978 version.
^{78) 79)}

More information on additional 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. ⁸⁰⁾
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. ⁸¹⁾

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).

^{82) 83)}

Outer Sprocket Cover(34863-79), polished, without kickstarter.
Click on a pic to enlarge: ⁸⁴⁾

Outer Sprocket Cover (34872-79), polished, with kichstarter.
Click on a pic to enlarge: ⁸⁵⁾
The master cylinder was mounted high on the 79's to miss the optional kickstarter shaft. Later models have no kicker. ⁸⁶⁾

Original Outer Sprocket Cover(34870-79), factory painted silver, without kickstarter.
Click on a pic to enlarge: ⁸⁷⁾

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

^{88) 89)}

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.
^{90) 91)}