I own a 1983 John Deere 750 compact tractor and it won’t start. It started fine until I installed a ROPS bar on it. Now, when you turn the key to start, you get nothing. It will start and run if I jump start it by crossing the ignition and battery terminals on the side of the starter. I’ve checked the battery (it’s good), I checked the PTO safety switch (it’s good), and I’ve checked the gear shift safety switch (it’s good). The seat safety switch is totally gone. The previous owner apparently disabled it. Any suggestions? Also, does anyone have a “layman’s” diagram or drawing of how the seat safety switch should be connected? I have the service manual, but I can’t make neither heads or tails from it. Thanks.