I'm intrigued: one of my carbs has the screw to limit how low the throttle slide goes at tick-over, and another carb, of otherwise the same model, doesn't.
To set tickover, the second one needs careful setting of the throttle cable, which isn't so precise. But, either way, the throttle slide remains just above the bottom, at the same height. How does this affect lubrication? Surely it's the same in both cases, limited to the small amount of oil in the "tickover" rate of fuel flow. No?