[quote=&quot;Rexalot&quot;:2g6jzh4n]May I inquire as to why you needed those measurements? Just curious as I had tying issues that resulted in tearing down the entire knotter stack on my 520 baler. I have the book plus some knotter guides that I used to set mine up.[/quote:2g6jzh4n]

My bill hook gear was jumping teeth and getting out of time and causing the shear pin to break.  Looks like the spacing between the bill hook gear and the cam gear was a little wider than it should have been, probably from years of wear. Some of the teeth are worn on the cam gear, but the bill hook and gear didn't look too bad. Fortunately I have new ones of those on hand, but my cam gear is excessively worn, and even if I re-shim the stack to get better engagement, I think it is going to cause trouble. I have bought a parts machine that appears to have good knotter parts on it. The knotter frame is cracked on mine from the bill hook being out of time, so I need that as well. I don't have an extra cam gear or knotter frame on hand, so that's where the parts machine comes in.

Just for giggles and grins, I called my local AGCO dealer, and all of the parts are available to totally replace the entire knotter assemblies. The grand total to replace both knotters for a 720... $5,800 and change. The look on my face, priceless.