OK guys, my mistake. When the drilling Slide Balance, I assumed (incorrectly) he was talking about the idle mixture screws.
I did some further research and found the following link.
http://members.aol.com/roundr1/CVK40.html
It appears the slide balance hole links the venturi vacuum to the chamber above the slide.
"As you advance the throttle cable that's connected to the butterfly valve, the butterfly opens to allow more air through the venturi. This increases the vacuum effect that is transferred up through the vacuum drilling (the hole you bored out for the Dynojet kit), on the diaphragm valve slide), that leads to the TOP diaphragm chamber."
The #40 drill (0.098"), enlarged, would allow the vacuum to be transfered quicker, therefore allowing the slide to rise quicker, exposing more of the taper on the needle, thus more fuel, etc.
"The top chamber is separated from the BOTTOM chamber by the rubber diaphragm. The bottom chamber is open to atmospheric pressure from the airbox by the crescent shaped
casting on the top of the venturi. When the vacuum in the top chamber rises sufficiently, the constant ambient pressure
of the lower chamber, helps the diaphragm valve overcome the downward force of the diaphragm spring, and it rises from the venturi.
As the diaphragm valve is raised from the venturi depression (lowest pressure area), the needle is pulled further out of the needle jet, exposing a thinner portion of the needle taper which allows even more fuel to rise into the venturi to meet the increased engine demand."
Perhaps this will add some clarity.
The #40 drill should work the same on a 1200 Trophy (4 carbs, 4 295cc cyclinders) as on a Sprintetc (3 carbs, 3 295cc cyclinders) and from what I can pick up the relative tune on the two is compatitable.
