Jims Catalogue

SHAFTS

The radius of the shoulder has been ground to a 16 or better finish to eliminate stress risers.

SPROCKET SHAFT HISTORY To help with the identification of Big Twin sprocket shafts, JIMS ® would like to provide you with a little history into the design of the sprocket shaft. From first conception to approximately 1954, H-D ® used a 6 degree taper on the flywheel side. In 1956, there was a change to 8-1/2” degrees, with a major diameter of about 1.060” at the largest end of taper. 1955 had a special sprocket shaft and flywheel, at 8-1/2” degrees, without a bearing shoulder on the shaft. The 8-1/2” degree x 1.060” taper lasted until 1972. It retained the 8-1/2” degree taper, but was increased in size to about 1.400” at the biggest part of the taper. This shaft also used a bigger nut,

*24001-72 - 1.400” *23909-80 - 1.310”

SEE NOTE BELOW

All sprocket and pinion shafts are precision manufactured here in Camarillo, California. We start with a special order of steel from an American foundry then saw, turn, mill, and grind all on numerically controlled machines. From saw- ing to the final phase of machining, each part is thoroughly inspected. After heat treating, all threads go through a special process to make them withstand greater torque stress. On big threaded sprocket shafts, approximately 50% more torque can be applied. All flywheel shafts are ground to a 16 micron finish or better unless otherwise specified. All ground diameters are concentric to within .0003” or less, to simplify all phases of flywheel truing and rebuilding. We strongly recommend using JIMS ® high performance nuts. When truing the flywheels the number of blows required, and how hard they should be struck depends on how far shafts are out of true, and how tight nuts are drawn. Always remove the flywheels from the stand and strike the flywheel rim at 90° to the crank pin. Use only a soft metal mallet. Never strike wheels while in truing stand. This could result in a broken pinion shaft or other parts and tools. THE FOLLOWING IS A QUOTE FROM THE HARLEY-DAVIDSON ® SERVICE MANUAL PINION SHAFT HISTORY The first non-splined, (tapered with key) pinion shaft was introduced in 1954. Taper was 6 degrees on flywheel side. This remained the same until 1990 with the introduction of the integral shaft flywheels. • 1954-72 Pinion shafts had the oil hole in flywheel and shaft, 135 degrees to the key (side oiler hole design). • 1973 Was the first year of constant oil flow to the crank pin oil hole in flywheel and shaft, 135 degrees to the key (end oiler design). • 1981-89 Pinion shaft was communized taper design. Oil hole in flywheel and shaft 90 degrees to the key (end oiler design). 135° EARLY • 1954 - Early 1981 has 3/4 - 18 thread on flywheel side. • Late 1981-89 has 3/4 - 20 thread on flywheel side. 6° TAPER KEYWAY 1-1/8” -16, and the flywheels still used a nut locking plate and screw until early 1981. In late 1981 they became what H-D ® called the “communized” taper, which is the old 6 degree, but with a size of about 1.310” at the largest part of taper. The flywheel side nut has the same thread at 1-1/8” -16, but the flywheels do not have a screw hole for a locking plate. *NOTE: All (-72) and (-80) sprocket shafts will have one of the above diameters. You can also check flywheels for this diameter to determine the right sprocket shaft for your application.

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