When swapping coils you need to check the North and South poles on the Flywheels Norm ,from memory the coil must be put on the E core backwards if you go from internal coil to external flywheel coil and reverse the coil when fitting an external coil internally.
A quick pic below to show how the magnetic flow can go through the front or back of a coil depending on internal or external coil or N S on flywheel.
