Sorry, not been on the message boards for ages. Only just seen your post. Been busy trying to mix maintaining/fixing the race bike alongside the rest of life :)
Funny that you would mention that in this post! I actually snapped a valve on practice day which caused lots of damage as you can imagine. Still had the stock CDI on so was not over revving it. I think there multiple contributing factors. High lift fast open fast shut cams and high millage valves and the fact I did the first round on stock valve springs. I went to check the shims just before the race weekend and noticed that one of the valves had got very very tight. Because the valve had done only one race weekend before it was last checked it seemed strange that it had tightened up after such short use. The theory I have to go with is that it was stretching which is why it needed such a small shim (at 2.60) to get the clearance right. It didn't take long to let go and although everything was a mess in the engine, the evidence shows that it snapped at the very top and then dropped down.
I have almost finished putting the engine together again with a set of 16 brand spanking new valves made to kit spec from a single block unlike the standard ones which are actually made in two pieces, the head and the stem (i believe friction welded). New overbored cylinders because the liner was damaged, new head because the valve punctured it and a new Wiseco piston for obvious reasons. All 4 pistons have new rings on as I will be running in again (this weekend). The next round is at Snetterton the following weekend. It's non stop at the moment :)
I damaged some of the lower kit valve retainers which is a shit because they are obviously rare items. I have found out that you can make up the equivalent of a kit 3 piece lower retainer with a stock lower one and the lower of the 3 kit piece retainers underneath it. The dimensions come out the same and because it is fixed at the bottom I don't have to worry about any differences in moving mass. Lucky for me because I have some spare of the very bottom kit ones. I would like to get the full set complete again just for resale value if anything. Probably will pester CCM soon because if I remember right, the middle and top parts of the kit lower 3 piece retainers are the ones he had plenty of ;)
If all goes well this weekend when I test ride it then I should be good for Snetterton where there will be no second chances for a bike not running right because the straights are sooo long there.
As you have already learnt, I was lucky enough that somebody let me borrow a spare GSXR SRAD for that race weekend. Its biggest strength is that it is so light for its age. I know the 7Rs are heavy, but I have done all I can to get the weight down and it does not come close to how light that bike felt. It was weighted at 172KG with oil in.
Full story is here if you are interested in the details :)