Ha ha, well Mike, I believe that the F2/3 top end problems were a little over-exaggerated, and quite easily fixed. My first F2 had around 30,000 miles on it when I bought it from the original owner who had maintained it meticulously, and it had a beautiful engine, showing no signs of top end problems. I wish I still had it.
My current F2 was an absolute POS when I bought it on EBay for 510 bucks, it had been crashed, in at least one fire, and left to rot outside. Not surprisingly, all the F2/3 "Gremlins" had manifested themselves in this engine, and due to the scarcity off parts for the black engines in 04/05, I used a K6 top end when I rebuilt it. I'm happy to see that there are plenty of good quality F2/3 top end parts available now though, so shortly I'll re-install the correct head and cylinders again.
I should say about now that I was very lucky that the old Greenspun site was full of very helpful, knowledgeable "F" guys like Mike Rieck who helped me out with some much needed parts, along with Sean Condon and a few other guys, because all I was able to salvage from my EBay "Bargain" was the frame, the wheels, and the bottom end of the engine, everything else was replaced. Here's an EBay "before" pic. It actually looked much better in the pic than what it was. Cheers, Terry.