IH: Engine Mechanicals

See also Crankshaft / Flywheel Tools in the Reference section of the Sportsterpedia.


Gearcase / Cam Cover

Cam Cover (casting 25202-52A) 1)



Commonized Flywheels

  • In May of 1981, the MoCo issued a bulletin stating that product and quality improvements have brought about a commonized flywheel taper design.

All tapers were communized at 6° and all keyways were standardized.
In June of 1981, an update to this bulletin was issued to include part numbers. 2) 3)

  • A limited number of E1982 XL engines (782216009-782237017) were assembled without the communized flywheel taper design. 4)
    • Notable component changes are included in the chart below.
    • This was a running change in 1340cc and 1000cc engines but both new and old designs were used in production until the old stock parts ran out.
    • Even though the assembly and disassembly was the same for the old and new style flywheels, the torque values did change for the new style assembly. However, new and old style components must not be intermixed.

Changes for Sportster 1000 engines include:

New Flywheel -
Sprocket Side
Gear Side


'Lazy 8' rear cylinder timing mark and no keyway
Single hole oil path.
The old style flywheel has a keyway on the sprocket side (23916-57A) and a compound (2) hole oil path on the gear side (23936-57A).
New Crankpin23960-80Oil hole is now 90° to the keyway
Old style crankpin (23960-54) oil hole was 110° to the keyway
New Crankpin Nuts23901-8120/1“ thread pattern at 150-185 ft/lbs.
Old style crankpin nuts (23967-54A) were 20/1” threads with 150-175 ft/lbs.
New Sprocket Shaft24000-80No keyway
Old style sprocket shaft (24000-75) has a large keyway
New Sprocket Shaft Nut23902-813/4“ x 20 threads at 100-120 ft/lbs.
Old style sprocket shaft nut (8011) has 11/16” x 18 threads at 100-120 ft/lbs.
New Sprocket Shaft KeyNot used
Old style sprocket shaft key (23985-12) has a large woodruff key (3/16“ x 1/2”)
New Gear Shaft24005-80One piece construction
Old style gear shaft (24008-75A) is of two piece construction
New Gear Shaft Nut23902-813/4“ x 20 threads at 100-120 ft/lbs.
Old style gear shaft nut (8011) has 11/16” x 18 threads at 100-120 ft/lbs.
New Gear Shaft Key11218Small woodruff key (1/8“ x 3/8”)
Old style gear shaft key (11200) has a large woodruff key (3/16“ x 1/2”)
New Crank Key11218Small woodruff key (1/8“ x 3/8”)
Old style crank key (23985-18) has a large woodruff key (1/8“ x 1/2”)

Roller Bearing Inspection (1957-1976)

  • In a letter dated May 9, 1977, an HD interoffice memo was sent regarding an inspection of parts stock roller bearings. Some roller bearing part numbers were found to have incorrect diameters. A new micrometer was purchased to remedy this problem.
  • Two of those part numbers are gear shaft (9421) and crank pin front rollers (9150A) for Sportsters.
  • In light of this oversight, a listing of part numbers with their correct dims and tolerances was issued as in below:
Used for 57-76 Sportster gear shaft roller bearingsDiameterSizeLength
9421.1876“ - 1974”Standard.800“ - .796”
9422.1878“ - 1876”+ .0002“.800” - .796“
9423.1880” - .1878“+ .0004”.800“ - .796
9424.1882” - .1880“+ .0006”.800“ - .796”
9425.1884“ - .1882”+ .0008“.800” - .796“
9426.1886” - .1884“+ .0010”.800“ - .796”
Used for 54-85 Sportster and K Model front crankpin roller bearingsDiameterSize
9150A.1875“ - .1874”Standard.480“
9152A.1877” - .1976“+ .0002”.480“
9154A.1879” - .1878“+ .0004”.480“
9156A.1881” - .1880“+ .0006”.480“
9158A.1883” - .1882“+ .0008”.480“
9160A.1885” - .1884“+ .0010”.480“
9161.1873” - .1872“- .0002”.480“

Crankcase Oil Strainer

  • If you've split the cases and the screen is in good shape, you don't have to take it out. Hit it with some compressed air and see if it needs replacing. 5)

6) 7)
The strainer is held in place by this pin. It is staked into place with the two horizontal lines radiating from the it. To remove strainer, you must first remove the pin. Tear the screen from the strainer and place pliers on the pin inside (the now destroyed strainer) and wiggle the pin out. Strainers and strainer gaskets are available for replacement. 8)

photo by ironheadjunkie of the XLFORUM http://xlforum.net/forums/showthread.php?t=1421916&page=2
HD Service Bulletin #M-829 dated May 19, 1981
HD Service Bulletin #M-829A dated June 12, 1981
HD Service Bulletin #M-840 dated October 2, 1981
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