yesterday was a fun day, not because i didn't learn how the safety switches and associated wiring intermix with each other, but because i found [i think, or at least hope] what appears to be the problem.
i started by locating all the switches and removing them from their mounting positions to allow access for testing purposes, both in action, as well as to confirm the wiring colors and the voltage and ground functions.
if you think laying on your head under your car's dash looking at wires is a treat, this tractor is for you !
i started at the brake switch. the first thing tested was the switch itself. it tested ok in it's function, so i next had my buddy run the key so i could check what was coming through the plug for the switch. the first thing that became apparent, was the starter tried to engage without the switch being plugged in !
there are two brake switches in this system, and i removed the wrong one. oops ! removed the correct one, the switch itself tested ok as to function, but was not seeing any voltage flow from the PTO switch.
next, the PTO switch was checked for function, and appeared to be operating as it should. a 12v jumper was used to send power to the brake switch, and when the brake switch was depressed, the starter kicked to life ! this is starting to look promising ! the wiring to the PTO switch was checked at the plug. the finding was battery voltage was MISSING in the crank position. with a 12v jumper on the switch, the brake switch was depressed, and the starter operated.
so on to the ignition switch. it has four wires, two red with white tracers [being hot at all times], the wire next to them [not sure of the color] being the run wire showing 12v in the run position as it should, and the orange wire [going to the PTO switch] being the battery voltage source in the start position.
with the ignition switch plugged in, the start position showed intermittent battery voltage, but i wasn't quite sure i was getting a good reading. at times, i was getting 2.3v, and at others, i was getting 11.8. so jumping the battery voltage at the plug to the orange start wire in the plug caused 12v to be sent to the PTO switch, which in turn, supplied 12v to the brake switch, when depressed, spun the starter !
so possibly the trouble all along could have been the ignition switch ?
this switch had previously been replaced before i got involved, and luckily, my buddy kept the old switch. it is plastic, so i popped it apart and discovered it was kind of melty, then i remembered i had done this previously. i grabbed the switch that was being used on the tractor [plastic as well] and checked for continuity. it had a reading at every time i jumped the hots and the key was turned to run, but the start position was not consistent, sometimes continuity, sometimes not. i tore it apart. it seemed a little dirty, so i cleaned the contacts up and applied a little white grease. i rechecked the switch in all positions numerous times, and it seemed to operate as it should. wow ! success at last !
i plugged it back in, and it cranked ! ...... for about a couple of revolutions, then quit ! i checked the wiring at the plug, and was getting battery voltage at three of the four terminals in start, with the orange wire going to the PTO switch reading 2.2v.
when jiggling the switch while trying to get a reading, occasionally, i could get the starter to kick, but not function.

so now, i'm ALMOST convinced the starter switch is, and has always been, the culprit. with the switch being plastic, i'm thinking i should obtain a universal type made of metal and make up a new plug to fit it.

NITROUSN, your wiring colors were spot on, so that helped me tremendously ! up bow boogie
what do you think about my ignition switch idea ?
it feels like i'm SO close........... luck
beer