Ok... let me think this through with you...
I thought all 68 110s had the Kohler with the magneto system and you were working to restore to factory configuration. That being said I would say that your 110 and mine would take the same switch. JDParts.com shows this as the proper switch for both tractors:
AM102543 SWITCH 1 - 130000 IGNITION (4 TERMINAL) (SUB FOR AM30771)
For tractors 130000 and above (does not stipulate engine or model year) it is:
AM31995 SWITCH 1 130001 - IGNITION (BRONZE) (5 TERMINAL)
That being said, I would say the switch is incorrect.
There are changes in the part numbers on the tractors above 250,000 too.
A quick interwebz search shows that AM102543 is the same switch used on the magneto 140 and this link might be helpful with your troubleshooting. http://www.yesterday...ges/143341.html says:
A 140 of that serial number should have magneto ignition, and there should be no connection between the 12 Volt electrical system and the ignition system, except a wire from the points to the ignition switch, that gets shorted to ground when the switch is turned off, to "kill" the spark, and thus the engine. Either you have this "kill" wire connected to the wrong post on the ignition switch, or you have the wrong ignition switch (one designed for a LATER tractor with 12 Volt powered ignition). The other possibility is that a burned "hot" 12 Volt wire in the harness is shorted to the ignition "kill" wire. If 12 Volts is being applied to the points, and to the magneto coil, the magneto coil is almost certainly "toast".
The CORRECT part number for the ignition switch on a 140 below S.N. 10,001 is AM102543. All the 140's prior to this serial number were originally magneto-ignition equipped.
Since these engines are magneto ignition, if the coil, points, and condensor are good, it should run for testing purposes with NO electrical connections to the tractor chassis. Of course, it wouldn't stop with the key, though!
I have a shop manual for these tractors, and, if memory serves, the info you need IS in there. I'll look tomorrow.
Me thinks a bit of wiring harness checking/repair and a new switch are in order to eliminate your electrical demons. Here is a WFM thread outlining similar problems with a 112 with the solid state ignition. It takes the same switch and harness. IF the harness is NLA from Deere then your only choice is to troubleshoot each section and repair as necessary since I cannot find a new one with a part number search and Hapcoparts does not sell them. This is good for me to know with my 110.
Edited by Trav1s, March 27, 2014 - 01:29 PM.