The voltage was 19.4 AC before the diode. I did not measure anything else as I think this might say what is wrong. The stator was new and so was the diode. Must be the flywheel? We did drop the flywheel on cement during the repair if that would effect it but it was not charging even before the drop. The whole thing (flywheel and magnets) are kind of rusty but I assume that must be typical. Does the space between the flywheel and pick up magnets matter terribly?
Wondering why you ask this? This is not adjustable. Doubtful your flywheel is bad if it has all it's magnets still inside.
You should have at least 24vAC at 3600 rpms with the charging system disconnected. This means the wire at the charge side of the diode is disconnected or open circuit voltage. You may have to use a tach and see if your engine speed is at 3600 rpm's when checking for 24vAC MINIMUM VOLTAGE.
Most of them twin Briggs has a adjustment screw at the throttle/governor linkage area to set the max rpm's at 3600 and I've seen them age to where the engine would not get full rpm's. I did not look at yours but you can check your Briggs engine service manual to re-search such. You can get a Tach for less than $20 now days. You might even try gently speeding up the engine manually to see how the AC reacts but be careful and do not overspeed the engine and make sure the red diode output wire is disconnected (open circuit) when checking the AC voltage as indicated on the wiring diagram. Any rpm's less than 3600 and the AC voltage will be lower.
Another thing you need to confirm is that you can read DC battery voltage at the diode cathode with the key on
and the engine not running. and again with the engine running This tells you that you have connection from the diode cathode all the way through everything to the battery and should get a charge or around 1 1/2 to 3amps at 3600 rpms if you get 24vAC.
I also would not trust the on dash ammeter right now, I would check the charge output amps with a low amp DC ammeter, like around 0-5 amps type.
If you have a low amps battery charger (0 to 10 amps or less) you can connect it's pos lead to the red wire at the diode area and ground the neg lead to chassis and when you turn on the mower's key switch compare your on dash ammeter to the Battery charger ammeter. You are using the stand alone battery charger as a test charge in place of your engine charging system. Just make sure you do not get the battery charger output leads reversed and for additional safety you could install a 5 or 10 amps fuse in the pos lead of the battery charger. Do not start the engine. This test will let you know that if you get 24VAC out of your stator and your diode is good you should get a battery charge indication on your on dash ammeter unless you have a bad connection at the diodes output at the plastic plug connector..:tango_face_wink:
You can connect you battery charger FIRST direct to the battery just to see the charge amps from the battery charger. (make sure the charger output is 10 amps or less when connected direct to the battery so as to keep from blowing the mowers in-line fuse which is probably 10 or 15 amps) when you go for the above test when connected to the diode output.