Right side carb slide not working on 88 1500

4 possibilities.
1) vent for slide stopped up
2)the hole for vacuum is stopped up
3) slides has pin holes in them?
4) the slides at top not in groove properly

Have you switched sides with the slides or just installed different ones?
Other that the "bead" around the top of the slide flat or not sealing maybe?

slide

I have an extra set of carbs and tried the slides from them. What vent are you talking about? What hole for the vacuum. Does the vacuum work thru the half moon shaped opening on top of the carb?

3 slides and not one works? Does it idle good?

Check that the sync bar is indeed attached by twisting throttle and looking for throttle plates to open on right carb. Then look for a big @ss vacuum leak or poor compression on R/side.

I had the same thing happen and mine was because the carb vent tube had come disconnected from the carb that the slide wouldn't work on. It's a fairly large vacuum line that goes to a T connector on the lower side of the carb on the rear side of the bike.