I have been riding a CB350K since the mid eighties and have at various times had slides sticking. Personally, I am not a fan of the original carbs. It is possible to fit after market slide carbs in place of the CV type. Many use Mikuni VM30, I have Amal Concentrics on mine. I have found the difference in responsiveness and tickover, starting, everything in fact to be much better.
I know this is not for everyone but might be worth researching and considering.
Also, I have a box of original carb parts which amounts to about four carbs altogether if anyone wants to make me an offer.