I have a Troy-Bilt Horse tiller I from 1975 left to me from my father-in-law. It has an HM80 on it. Whenever I wanted to shut it off, I would throttle it down and it would die out. Just cleaned and rebuilt the carb. Now when I throttle down it just idles slowly. I'm having to choke it out to get it to shut off. Can I just keep doing this? Is there a better way other than installing a kill switch? Idle restrictor screw is all the way in. Same place it was before I cleaned it. Does not have a high-speed adjustment.