It's a rare thing for the slide to jamb due to over tightening and flange warping .
Remove the carby ad take the slide off the cable and insert the slide whilst looking through the venturi (? spellcheck doesn't recognize "venturi" !) ~ the slide *MUST* easily slide up and down of it's own weight .
Resist sanding the slide and bore ! .
*IF* the slide drops in and out easily of it's own weight, use a sharp object to *carefully* remove the O-Ring in the flange then place a piece of 1,000 grit (no lower / coarser !) wet dry abrasive paper on a piece of flat glass (I've used door windows in the field) and give it a single figure eight movement, turn the flange up and look at it ~ usually the outer edges will now have a slight sheen where they touched .
If so *gently* work the flange in a figure eight motion stopped frequently to check, the *instant* the center of the flange shows ANY brightening, STOP clean it yet again and replace the O-Ring being sure to flip it over so it'll seal properly .
I like to use flat steel 6MM washers under the nuts, this helps reduce warping .
If the slide doesn't easily slip in and out again, wipe it and the bore clean with white paper towels then spray the slide with some silicone spray and slide it fully in with your finger ~ slide it back out again and any high spots will be shiny .
Serious time and care must be taken here as it's very easy to ruin the carby by abrading it whilst trying to make the slide move easily .
I hope you know to *gently* lift the needle to ensure the 'W' clip is fully seated home ~ I find a lot of carbys that the needle is free to move up and down a few MM and this guarantees hard starting and poor running .