Iron Sportster bill of material


Blog BOM Custom Design
Garage OSARM Repair Smörg

Primary cover

The 1952 Harley K-model was the the first motorcycle that Harley made that had a sprung rear suspension. It was also the first adaptation of "unit construction" where the engine and transmission was in one case. That one case had a primary chain between the engine and transmission. In 1957 the K-model was renamed the Sportster in honor of its overhead valve cylinder heads. This cover seals up the chain and clutch. The chain runs wet, in an oil bath. The earlier dry clutch was sealed from this oil. In 1971 the engineers designed a wet clutch system.

34951-52


 Sportster_Engine_Primary_Primary-cover_32951-52_Primary-cover_1952-1953 alt text CAD
Blueprint
The primary cover encloses the drive chain that connects the motor and transmission. It mounts on the left side of the engine. The clutch is built into the transmission sprocket. This is an aluminum sand casting. Casting number 34950-52. Finish is natural as-cast. Harley may have polished the longitudinal rib that runs from the front to the rear bolt holes. The two outer screws are shorter 1/4-20 countersunk Cadmium-plated. The center bolt is longer 1/4-20, and ties into a threaded boss on the transmission trap door. The gentle divot in the bottom clears the left footpeg. There is a boss for an oil level or oil drain hole rearward of the divot. Harley never drilled and tapped this boss. At the rear is a boss that mounts the brake switch. The oil fill cap has a hole in order to vent the transmission and primary. Problems: No way to check oil level. Sand casting may be porous and weep oil. Vent hole lets water in if you pressure-wash the bike. The rear brake is a chassis system so the brake switch should be on the chassis. When you drop the bike, the brake lever scrapes or pierces the cover.

34951-54

 alt text alt text
Similar aluminum sand casting. Casting number 34950-52A. Boss behind footpeg divot removed. Boss for oil level hole added in front of divot. Semicircular divot added near brake switch boss to clear the brake lever return spring. Problems: Sand casting may be porous and weep oil. Vent hole lets water in if you pressure-wash the bike. The rear brake is a chassis system so the brake switch should be on the chassis. When you drop the bike, the brake lever scrapes or pierces the cover.

34951-57

 Sportster_Engine_Primary_Primary-cover_34951-57_Primary-cover_1957-1966_ Sportster_Engine_Primary_Primary-cover_34951-57_Primary-cover_1957-1966_
Similar aluminum sand casting. Casting number 34950-57. "Sportster" logo embossed on the longitudinal rib. Front part enlaged to clear compensating sprocket, and internal boss added to retain sprocket if it comes loose. Date code added to the inside. Date code perhaps used by factory to track porosity problems. Problems: Sand casting may be porous and weep oil. Vent hole lets water in if you pressure-wash the bike. The rear brake is a chassis system so the brake switch should be on the chassis. When you drop the bike, the brake lever scrapes or pierces the cover.

34949-58

 Sportster_Engine_Primary_Primary-cover_34949-58_Primary-cover_1958-1963

Steel stamping. Separate steel stamping for ribbed clutch area is pressed on over main stamping. Multiplicity of straight-slot fillister-head 1/4-20 bolts, plus one 10-24 screw at the bottom. Tapped hole for oil level. Oil fill cap uses cork gasket and held with two countersunk screws. Problems: Thin metal at bolt holes deforms under moron torque application and cover does not seal. Same moron uses silicone sealer, which gets into roller bearings and seizes transmission. Odd-ball 12-24? screw at the bottom. Cannot use compensator sprocket with this cover. Oil weeps past two cap screws. Rear brake switch uses small piggyback bracket in earlier models that changes thread engagement of two bolts at rear. The rear brake is a chassis system so the brake switch should be on the chassis (moved to swing-arm in later models). When you drop the bike, the brake lever scrapes the cover. Curious enthusiasts wonder how the tranny vents with this setup.

34949-64

 Sportster_Engine_Primary_Primary-cover_34949-64_Primary-cover_1964-1969 Sportster_Engine_Primary_Primary-cover_34949-64_Primary-cover_1964-1969
Same as 34949-58 cover, only chrome-plated. Same problems.

34947-67

 Sportster_Engine_Primary_Primary-cover_34947-67_Primary-cover_1967-1969 Sportster_Engine_Primary_Primary-cover_34947-67_Primary-cover_1967-1969
Improved sand casting or investment casting. Used on electric start models. Hence boss on inside with Torrington bearing that accepts the electric starter shaft. Small dowel pin near needle bearing to locate shaft. Cover clears compensator sprocket that you must use or the Bendix will crack. No date code on inside, perhaps since porosity not a problem with improved casting method. Squared-off divot to clear footpeg. Oil level now straight-slot screw. Vented oil-fill cap used to vent transmission. Problems: Multiple length 1/4 bolts and that odd-ball 12-24? screw at the bottom.

34948-70

 Sportster_Engine_Primary_Primary-cover_34948-70_Primary-cover_1970 Sportster_Engine_Primary_Primary-cover_34948-70_Primary-cover_1970
Same casting as 34948-67, but not drilled for electric starter shaft Torrington bearing. Small dowel hole near bearing area also not drilled. This was used on one year only, the 1970 XLCH model, perhaps because Harley no longer wanted to have one case for the XLCH and a different engine case for the XLH. Same problems as 34948-67.

34948-71

 Sportster_Engine_Primary_Primary-cover_34948-71_Primary-cover_1971-1976 Sportster_Engine_Primary_Primary-cover_34948-71_Primary-cover_1971-1976
Aluminum die casting. Expensive tool may be due to the 1969 AMF (American Machine and Foundry) takeover of Harley and the pouring in of large investment monies. Accommodates the wet clutch setup. Hence a second non-vented cap is placed over center of clutch area. Complex cast area inside to hold ball-ramp clutch release mechanism. Phillips-head 1/4-20 blots. Phillips-head odd-ball screw at bottom. Oil fill is also Phillips head. Clutch cable treads into cover and hooks on mechanism under cap. Electric start models have Torrington bearing and dowel pin, kick-start XLCH models do no have this loaded. Problems: Different length bolts and that odd-ball screw. Clutch will not operate with the cover removed. Vent hole in cap and clutch cable hole lets water in if you pressure-wash the bike. When you drop the bike, the brake lever scrapes or pierces the cover.

34948-71B

 Sportster_Engine_Primary_Primary-cover_34948-71_Primary-cover_1971-1976 Sportster_Engine_Primary_Primary-cover_34948-71_Primary-cover_1971-1976
I invented this part number since it looks like there were black-painted covers, but I can find no call-out in the parts book. Maybe enthusiasts just painted these themselves.

34949-75A

 Sportster_Engine_Primary_Primary-cover_34949-75A_Primary-cover_1977-1978 Sportster_Engine_Primary_Primary-cover_34949-75A_Primary-cover_1977-1978
Aluminum die casting. Provides for new engine cases in 1977. Removed the odd-ball screw at the bottom and added a 3/8 stud for the adjuster mechanism at the bottom front. Added yet another hole on bottom of cover to pass 5/16 chain tensioner adjustment bolt. Oil fill cap no longer vented, vented bolt added at top of rear motor mount to vent tranny. Bronze bearing and seal for gear-shift lever. Large hole in center for large stud that mounts the foot-peg. Hence no square divot to clear frame-mounted footpeg. Cover located by hollow dowels at front and rear bolt holes, so no small dowel for electric-start shaft. Problems: External chain adjusting system more trouble than its worth. Different length bolts and that odd-ball 3/8 stud. Oil weeps out of stud, adjuster hole, clutch cable entry hole, and footpeg stud hole. Clutch will not operate with the cover removed. Clutch cable hole lets water in if you pressure-wash the bike. When you drop the bike, the gear shift lever scrapes or pierces the cover. The footpeg is a chassis system and should be on the frame.

25430-81

 Sportster_Engine_Primary_Primary-cover_25430-81_Primary-cover_1979-1984 Sportster_Engine_Primary_Primary-cover_25430-81_Primary-cover_1979-1984
Identical to 34949-75A but polished. Same problems. Harley never offered chromed covers on Iron Sportsters, these are aftermarket items.

25424-80

 Sportster_Engine_Primary_Primary-cover_25424-80_Primary-cover_1980 Sportster_Engine_Primary_Primary-cover_25424-80_Primary-cover_1980
Identical to 34949-75A but painted black. Same problems. Image and information credit: Jan Willem Boon - parts for your Harley-Davidson - database

25424-81

 Sportster_Engine_Primary_Primary-cover_25424-81_Primary-cover_1981-1982 Sportster_Engine_Primary_Primary-cover_25424-81_Primary-cover_1981-1982
Identical to 34949-75A but painted black and ribs added across middle. Same problems, but less susceptible to being broken by gear shift lever when you drop the bike. Image and information credit: Jan Willem Boon - parts for your Harley-Davidson - database.

25433-83

 Sportster_Engine_Primary_Primary-cover_25433-83_Primary-cover_1983 Sportster_Engine_Primary_Primary-cover_25433-83_Primary-cover_1983
Identical to 24424-81 but aluminum finish. Same problems.

25439-83

 Sportster_Engine_Primary_Primary-cover_25439-83_Primary-cover_1983 Sportster_Engine_Primary_Primary-cover_25439-83_Primary-cover_1983
Identical to 34949-75A but painted ivory off-white. Used on XR-1000 models. Same problems. Image credit: Jan Willem Boon - parts for your Harley-Davidson - database.