I actually had this issue on a high grade Nording that I bought used. There was a kind of defect when the stem was drilled that made it so that bits of cleaner would clog one of the openings whenever I would clean it, and it was getting to be a real pain in the butt. At the suggestion of someone much smarter than I, I sent it off to a repair guy to have the stem re-drilled, which he did for a modest $10, and it smokes much better now. Something to think about if you have this problem in the future.