Excellent write up, Max. Anyone considering switching out their gas cap will now have everything they need to complete this job with confidence.
You are welcome. It should also be extremely helpful even if you don't want to switch a cap, but just repair or clean your existing one, or put it back together correctly. I find it amazing zero info like this was available anywhere.
The irony is, I was unwilling to mess with the cylinder in the old cap without having a replacement cap for fear of messing things up and being left with an unridable bike for a long time. But the problem really was mainly the cylinder and not the latch. And that was reused and not new. It was a reasonable mistake considering that in the past, most of my problems really were with the latch. Yet I don't regret the decision.
1) I didn't mention it in the document, but the vent hardware in my old cap was quite messed up. The teardrop plastic part that is supposed to move was "welded" down and couldn't be removed at all. So that might have been dangerous.
2) Certainly the latch was far from ideal, and now it is new.
3) Some of the filler ring was cosmetically messed up from springs on gas pump nozzles, so now it is pretty again (and I hope to keep it that way).
4) The main seal was pretty worn, so now that is new.
5) The cylinder cap and seal were really bad in the old cap. So now those are new, and were contributing to much of the problem with the cylinder.
6) I learned a lot and have more spare stuff at my disposal.