Tapered Roller Bearing conversion for the Steering Head

Here are some notes and pictures of a kit to convert the steering head bearings of a Moto Morini 3-1/2 to tapered roller bearings. I purchased this kit from Wolfgang Tritsch. This kit uses identical bearings and retainers, top and bottom. The bearing outer race is marked:SKF 639172, with an additional marking "S". The bearing itself is marked SKF 439174 - it also has the code "W39 S" on it.

The retainer is shown in the following two photos

Some approximate dimensions:

Outer diameter of the bearing holder section: 60 mm.
Wall thickness of the bearing holder section: 4 mm.
Outer diameter of the steering head stem section: 36 mm.
Inner diameter of the steering head stem section: 28 mm.
Wall thickness of the steering head stem section: 4 mm
Overall height: 34 mm (16 mm in the bearing holder, 18 in the steering head stem section)

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