does the 175 ones fit
take a PE175T and lift the stator, rotor and CDI and drop it all in. voila! job done.
If you REALLY want a PE400 rotor, they are either bloody expensive or not available.. they had 33% more mass, but when they re-jigged things, it must have hit some harmonic, whereby the magnets tended to crack or destroy themselves. Maybe it was just lousy glue.
In any case, ALL the earlier PE's (175 and 250) happily ran with the lighter flywheels and I once had a functioning PE400 engine on my bench and found it too had the 175 stator and rotor fitted at some time.
Luke