Fix for OS-91 SZH Fan Run Out on Stratus

[Alfred]

It's the inside where the ball goes that is the most importened. The others are partially compensated by the 2 dampers and the Fan/clutch gap.
Do it just like in the photo and go for maximum accuracy you can get.
By the way, a metric Dial Indicator will give you a higher resolution.

[saary]

what is the maximum acceptable runout i can have inside the fan hub?

[Mercuriell]

I've just assembled and dialled in two fan hubs on BW Special Stratus' - no way would it dial in less than 2.5 thou unless I drilled out the outer recessed collet to 8mm to make it looser on the threaded crankshaft. I also burnished the smooth first bit of crankshaft so that the inside collet was a firm but sliding fit - doing this the hub was adjustable during nut tightening and I got the run out down to less than 0.8 thou.

[Ed W]

The easy fix to the fan/collet problem is to buy the Maryland Machine fan and spend your valuable time doing something other than tinkering with the fan.
Ed