Cv carb

Actually if you ask anyone in the tuning business they will flat out tell you to
never ever drill the hole out to a larger size EVER!

What happens is the hole gets larger and the slide hunts for a good stable point for
smooth throttle, also as the slide comes up, if it comes up faster the needle comes up faster allowing for more fuel.

You might take a same size bit and clean up the hole if it was not properly machined
but NEVER drill it out to a larger size.

i have to agree.............drilled one once........never could get the settings correct.

Drilling the slide out that large may slightly improve initial throttle response but overall performance would suffer. The slide would try to close just as fast as it opens, and flutter terribly while decelerating. This makes tuning difficult to dial in. Whenever I have seen a slide port drilled this large I have tossed them out and started over with a new one. What amazes me is that there are still commercially available tuning kits such as Dynojet who still have this outdated step in their instructions. My recommendation has always been that if you're going to drill then don't go any larger than 7/64 which will clean up the original port. A port of 1/8 or larger is a problem.

And for anyone who doesn't want to drop $45 on a new slide here is a ghetto way to fix an over-drilled slide.
1. Fill the oversized hole with JB Weld, make sure it cannot come out.
2. Drill a new 7/64 hole to the left or right of the filled hole. The slide will function the same even with that hole off center.
I can't stress enough to make sure the filler in the hole cannot come loose. You don't want that piece sucked into the engine... and if it does let me just say right here, I'm not liable for any damage to your engine.