My new to me, used GT2550 has me puzzled. I can start the engine with the PTO in the off position, but the blades start turning when it cranks up. I can pull the PTO switch to the ON position, but the blades stop turning. It's like the PTO clutch is wired backwards. The wiring connectors are one-way and cannot be turned around. I was wondering if someone in the past had changed some wires in the connectors. HELP!??