Two weeks ago my 6 volt positive ground TO20 tractor started well and ran fine. Today I went to start it and no luck. I charged the battery to a full charge, and the starter turns the engine over nicely now. Pulling the coil's hi voltage wire from the center of the distributor cap and holding it close to the engine block while cranking the starter with ignition switch on, no spark jumped to the block. Pulled other end of wire from coil tower and checked continuity from end to end and was fine at zero ohms. Checked voltage between each of coil"s primary terminals and engine block, and also at distributor with points open, and all 3 were the same at 6.3 volts. Points and condenser have less than 12 hours service time on them, and points looked fine. Checked point gap and was correct at .022, removed condenser and bench tested it with an analog multimeter and it does appear to charge and discharge okay. Re-installed condenser, and with ignition switch on and points closed I manually opened and closed the points several times using an insulated tool, but there was absolutely no visible arcing whatsoever. Swapped condenser with the last one, which had worked fine, and still no arcing. Swapped coil with a new 6 volt replacement coil that I keep on hand, and no difference observed. Checked all wiring and it is good and connected as shown in TO20 service manual. Got dark, so I came inside to think about it, do some Internet research, and to write this. Knowing that the voltage is fine at the coil and the distributor, it would seem that amperage is low or I would see some arcing at the points as I did when I last replaced them. As stated earlier, the battery took the charge well and is cranking the starter nicely, so definitely not a low amperage battery. Tomorrow morning I'll try running a 12 gauge wire directly from negative battery terminal to coil to bypass the ignition switch, but if the problem is not the ignition switch then I will have tried just about everything I can think of and will hope you folks can give me further suggestions. Incidentally, the ignition switch on this tractor is not a key switch. The old key switch was removed by the previous owner when it failed, and it appears that he utilized the on/off toggle light switch (with no lights hooked to it) as an ignition switch, which has worked fine. In checking the wiring, I did remove the wires from the switch and tested the switch with an ohm meter, and it checked okay - open circuit when toggled off and zero ohms when toggled on.