Okay, now for an update. I found a new tappet cover online at Hitchcock's and received it in only 5 days. The original cover was too cracked to even attempt the JB Weld fix. I cleaned, sanded, scraped and carefully installed the new cover and gasket. Now the frigging bike won't start! It cranks easily, it has fresh gasoline, a new spark plug and putted for a few seconds a few times. Now it just cranks. Any ideas?
Relative to what Arizoni has asked you about the decompresor permanently holding the exhaust valve open, it doesn't seem likely, BUT
(1) Did you have any issues installing the operating lever and cam in your new tappet cover?
(2) When you pull up on that little lever (with the spring on it) on tappet cover with your finger, does it move up and down?
(3) When you operate the handlebar lever does the little lever on the tappet cover move up and then down when you release it?
If (2) and (3) are yes, then I don't believe the cam is jammed into the exhaust valve push rod. If that little lever in moving up and back down freely, I don't think the cam could be jammed.
But I 'spose anything's possible.
So. Is your battery really charged up to tip top shape?
Have you pulled the plug to see if it's wet with gas? Or fouled (dirty black)?
Petcock? Kill switch?
You could also remove the tappet cover altogether and see if it starts.