Jims Crankcase Lapping Tool for Harley-Davidson

Used to lap the pinion bearing race on the right crankcase.

Removes more material in less time, but with greater precision than a conventional lapping machine.

The JIMS lapping machine is guided on both sides of the pinion bearing race.

This additional support on the cam gear side of the track is achieved by a bolt on the base plate that precisely secures a drill bushing in which the lapping machine rotates.

This base plate is located on the same pins on the engine housing as the cam cover.

The position of this drill bushing is held 0.0002" from the engine case pins and 0.0002" from the case centerline.

Now, instead of guiding only from the left side with Timken bearings, which are floating fit, the JIMS lapper uses a specially ground bearing sleeve to hold the left side of the lapping shaft stationary.

Both ends of the lapping machine rest precisely on the same centerline as the flywheel assembly. Thanks to this extremely rigid configuration, the lapping machine can be driven with a low-speed drill motor without fear of vibrations in the lapped bearing race.

The JIMS lapping machine can also be operated with a conventional hand crank when desired.

It is recommended to use JIMS 978341 (retaining ring removal and installation tool), especially on 90-99 model crankcases.

Note: See 978412 for 1-3/4" OD replacement lapping head.

Fits: 58-99 Big Twin crankcases (except Twin Cam).