Magical Disappearing Main-Jets

While I wait for Joey's center-stand stopper and cam cover tachometer oil seal to arrive, I decided to yank the carbs and figure out why it's having such a hard time at 3/4 to full throttle.

I hung the carbs so I had both hands free then drained them.

Then, I popped off the first float bowl and found this:

Where'd the main jet go?

The main jet pulled a Houdini and disappeared. Luckily I found it hiding under a nearby mason jar lid.
Carbs 1, 2, and 3 all had the same problem. Carb #4 still had the main jet in.

I'm not really sure how 3 main jets managed to back themselves out, but I'm glad I caught that. This time I was certain to torque them down really well. I'm not entirely certain this will solve the problem though. The bike was having the exact same issue before I swapped out the main jets from 110 to 120.
This time, I put 125's in all four carbs to be sure. I'd rather it be a little too rich to start than too lean. I'll sort out the details later but I'm suspect that with the stock airbox and the 4 into 1 exhaust that's on there now, I'll probably settle on a 122.5.
A quick plug chop will determine what the appropriate jet size once she's back up and running. Hopefully the stock #40 slow jets are still appropriate, since I don't have any screw-type #42's lying around.