It's a wonder it ran at all with that tap. They suck a lot of fuel under acceleration and my Spitfire MkIII would die unless both taps were open. Those barrel marks are probably a minor nip up - pretty common if running hard and long in very hot weather with newish pistons. I've had it happen a couple of times in over 100F temps and a hone will sort it out. While the barrels are off have a good look at the cam and followers as I've seen them wear out quickly on some bikes, and also check the movement in the rods for bottom end wear. If there is any rocking at all (a bit of lateral movement is OK) then the shells are probably shot, also a common problem. Personally I'd replace the pistons with a set of JP or other lower comp jobs and give the bottom end a bit of an easier time. Be careful with that centre-rear rocker cover stud as the hole is bored straight into the oil gallery and if it comes loose in the head it will piss oil out around the nut. I'd also take the right hand cases off and run a wire rod through the breather hole in the cam as crud can build up in there and partially block it. And until you split the cases and clean the sludge trap, don't use multigrade detergent oils or the crud will come out and grind the guts out of it in a very short time. I had what was supposedly a fully rebuilt "new" engine in the Spitfire destroy every bearing in less than 500 miles as the cretin who had rebuilt it didn't bother cleaning the trap.