Well it sounds like we have a party mix of problems going on with this one.
The not starting issue has nothing to do with the clutch as long as the clutch is not locked up.
Did you replace both bearings or only the one in the pulley?
The triangle shaped piece is the clutch brake. I serves two functions, 1st it stops the blades when the PTO is turned off, 2nd it is used to adjust the air gap.
The air gap needs to be adjusted to the proper setting so that the armature is at the proper distance from the rotor in order for the coil to be able to pull it into engagement. You end to adjust it evenly with a feel gauge through all 3 slots. This thread will give you a little more info.
http://www.onlycubcadets.net/forum/showthread.php?t=30
#2 driving hub (rotor)
#3 driven disc (armature)
The pulley is not supposed to spin freely, it's stopped with the power to the PTO in the off position and it's connected to the engine and rotating in the on position.
If I had to guess I think you have the air gap screwed up.
Now as far as electrical goes. You need to find out what is going on. How long have you had to jump it at the solenoid?