Does the wiring going to the stator have a "lumpish" sort of bulge near the plastic wiring connector?
If so, the replacement engine features the "unregulated" 3 amp Dual Circuit charging system.
If this turns out to be true (about the lump) I hope you got a great price on the acquisition of this mower cause you will need to purchase at least a stator and regulator to upgrade the engine to the 9 amp system the tractor was manufactured with.
Adding a regulator to a Dual Circuit system (hoping for higher amps) would be futile because that charging system only outputs 2-4 amps maximum. Regulated systems use a much larger stator and regulate DOWNWARD. You can't regulate UPWARD, you gotta have something that makes excess energy and then pare that down to the correct level.
Post the actual model number and type number of the engine that is now on the tractor.

".....I checked the stator voltage and got 25 volts....."

The "other" end of the wire should be the VR, if this engine has one.

Can you take a pic of the connector and post it?

Does it look like mownies pic in the thread I linked to?

Here is a link that might be useful: mownies link

This post was edited by bill_kapaun on Sun, Aug 4, 13 at 13:46