The B/C/N 250's shared the 175 stator and flywheel. (yes, ALL the 175's). Regardless of what anybody says, that stator and flywheel will fit every PE.
32101-40521 PE250B/C/N, PE175C/N/T/X/Z/D/E, RS175T/X/Z
the T/X/Z PE250 and PE400 had the 33% larger (mass) flywheel (which is only 100 grams heavier than the earlier ones) and widened stator to suit. It was also rotated 90 degrees. No idea why. Perhaps just easier to access the slots during assembly,
The coils are all 'new'. Visually however, very little difference. For some reason, this larger flywheel had a history of letting go of its magnets, so it is becoming a bugger to find a good one! (I have a 250X and a 400T on the floor - both missing their flywheels)
Flywheel PE 175 N 1094 gramms 107 mm OD markings: FP 5153 and 4192
Flywheel PE 175 T 1094 gramms 107 mm OD markings: FP 5153 and 4192
Flywheel PE 250 T 1192 gramms 119 mm OD markings: FP 4172 and 4192
Flywheel PE 400 T 1192 gramms 119 mm OD markings: FP 4166 and 4192
So - MANY people did the simple trick of using the 'old' lighter/smaller flywheel and stator.
It has been said that you have to rotate the old one 90 degrees and drill new mounting holes.
However I know of a 400 running just fine with a 175 flywheel and stator dropped straight in.
See a photo that shows the rotation of a PE250X stator beside a PE175N stator here:
http://cid-407d7ef0965d3991.skydrive.live.com/self.aspx/Pure%20Enduro/STATORS/T%20vs%20N.jpg Luke