Carb slide sticking
I had the same problem with my 21BB slide carb.You gotta make sure you oil it after each run.I had to pry mine loose with a screw driver a couple of times it was stuck so bad and then tap it back in with a small hammer(not recamended).Take the linkage off and twist the slide to the left or right(like a screw) and push it in at the same time.It has a spot that it gets hung up on and when it does it is really hard to get loose again.Also remove the rubber boot and spray some wd40 on the shaft and just keep working it back and forth bye hand and maybe try some after run oil instead of the WD40.Hope this helps it did with mine.