Small Engine Troubleshooting Problems? Ask a Mechanic Now.
You have two wires going to your pto clutch. One wire is red/orange and the other one is black. Your black wire is a ground, and the red/orange wire is your positive wire. Let's try something. Check your battery voltage with your ignition switch, and your pto switch off, then check it again with your ignition switch, and your pto switch on. We need to determine if your battery voltage is dropping too low to operate your pto clutch.
You stated that voltage appear to be getting to your clutch, but soon drops. We need to determine what the voltage readings are, before and after the voltage drop.
Click on the link to open up the wiring schematic I have attached for you. We can use it as a reference.