Small Engines (Lawn Mowers, etc.): John Deere R72 PTO, john deere r72, hands and knees

Question
I recently acquired a Deere R72 RER. After getting it running, I couldn't engage the pto... moving the lever did nothing. After running a while, I was slowly moving the lever back and forth and the blade engaged. WELL, that's great, but I can't disengage them now... if the engine is running, the blade is turning. Have you ever heard of this? What should I do?

Answer
Get down on your hands and knees and take a look. If you can fix it, it will be obvious. There's like 3 moving parts.  If it's not obvious to you, you can't fix it.

When I say obvious I don't mean to be rude.  The obvious I'm talking about is, for example, my toaster isn't working. Of course not, it's not plugged in. It will be that obvious.