I have a 2004 Honda VT1100C Sabre that I recently rejetted and now has what I consider a major problem. I can't seem to get the mixture screws to stay in. I 'lightly seat' them as recommended and then back them out three rotations. At three rotations the screws turn freely when the engine is revved, and will work themselves all the way out. Then the motorcycle runs very rich. At one and a half turns our it runs lean, and they will still slowly work their way loose. One of the screws is new, to the tune of 500 THB. What exactly does 'lightly seated' mean? Maybe this is where I'm not getting it. I've got a K&N filter and a free-flowing exhaust pipe so I needed the rejet. But right now I feel screwed!

Here is a little trick you can try, Once you get the mixture screw set where you want it, get some fingernail paint ( that stuff the girls use to colour their nails ) and put a little paint over the screw and housing, let it dry ( a minute or two ) This should stop the screw from moving and will easily crack and flake off if you need to re-adjust the screw.
Are you sure your new screw is not meant to have a small O-ring fitted ? Its not usual that the mixture screw will move under normal running conditions.
Hope this helps
Matt.

Exactly what I wanted to ask – did you remember to put the springs back on the screws? The air screws are installed with a little O-ring and a protective washer against the body of the carburetor, and a spring to keep the screw from changing its adjustment. Lightly seated means it won turn any more with the pressure of two fingers on a appropriately sized screwdriver. Those (stock Keihin) carburetors have plugs pressed in to keep you from changing the adjustment from the stock lean settings. If you're not careful removing them, the carburetor bodies could be damaged. I can't see, though, how any damage done removing the plugs could cause the screws to loosen. Nope, it sounds like the tension springs are missing. If you need to the screw out more than two and halve turns, you should install the next size bigger low-speed jet.

By the way the nail-polish advice from Matty is a marvelous idea... it's cheap and is available everywhere... I bet most of us not even have to leave the house to get some...

By the way nail-polish is also a great product to touch-up stone chips damage on your motorcycle...

As has been said it should have a spring. see part #5 in link above

Any decent bike shop should be able to help as the springs are quite common. Or you could flick through the Honda Parts books and find something.

Live in the sticks? A drop of superglue on a pin right at the junction between the screw and the carburettor. Same principle as nail polish but stronger and instant. Can be removed or softened enough to undo with Nail polish remover (acetone). NB Keep acetone away from paintwork