Hi, I hate to keep on, but I still believe I'm missing something. The OEM manual describes the procedure for changing the tensioner rail as:
1. remove upper guide on right head;
2. remove tensioner;
3. Remove sprocket; 4. remove pin, then tensioner rail, etc. etc.
OK, I can't get the two left upper guides out past the sprocket and chain, though all 4 pins are out. The manual implies the guides can be removed without removing the tensioner or the sprockets, so seems like there is a way, but I haven't found it. My original plan was to change the three upper guides, then bar the new chain in, then change the tensioner and tensioner rail. Thanks everyone.