Done repolarizing the generator, didn't fix the problem.
I think it's the regulator. Here's why. This tractor's regulator has 4 tabs,
A = armature
F = field
BAT = battery
L = load (lights)
A and F are connected directly to A and F on the generator. BAT gets +12V from the battery, not directly, but through the Amp meter.
Now, L from the regulator provides +12V to the ignition switch (key), which distributes it, depending on the key position. Key positions:
0 = tractor is off, no power goes to any part of the system.
1 = headlights get +12V
2 = headlights, and high voltage coil get +12V
3 = this is spring loaded and it goes back to position 2 if you let go of the key. This supplies
+12V to the solenoid which in turn opens the high current circuit from the battery to the A (armature) of the starter/generator, thus turning the engine. So if you let go of the key once the engine started, ignition switch goes to position 2, which supplies a continuous +12V to the coil which supplies the high voltage impulse to the spark plug.
Fine, here's the issue. When I put the key to position 3 to start the engine, the voltage supplied by L from the regulator goes to 0V. So this makes me conclude that something is not right with the regulator.
The other hokey thing with this tractor is the following. I bypassed the regulator and supplied +12V directly from the battery to the solenoid. The engine does start, not just turn, but runs for real; but as soon as I remove the jumper to the solenoid it stops. This again points to a defective regulator. I think. Please correct me guys, if I took a wrong turn somewhere.