So, I dunno if you've resolved this problem or not but I'd like to chime in. First off, I'm not a licensed mechanic but my father and grandfather taught me at a young age how to work on things. I have done my own repairs most of my life and consider myself somewhat mechanically inclined. Back at the start of summer I removed my carb, totally disassembled it, soaked it in carb cleaner for two days, rebuilt it with a brand new rebuild kit, reinstalled it and immediately experienced the same thing you're describing. My problem was the throttle butterfly. There are two round plates that slide into the split shaft and are held in place by two small screws each. One would think that being round it wouldn't matter which plate went where or how they were oriented, but that wasn't the case on mine. If you remove the spark arrester from the carb and look down past the choke plate to the throttle plates they should close off COMPLETELY when the throttle control at the helm is in neutral. I had an ever so small gap and I suspect you may also. I also could give the linkage a little nudge or snap the throttle and it would idle down but otherwise it idled around 1000-1100 RPM. After removing the carb and disassembling the butterfly I mixed and matched and flipped/flopped the round plates in the shaft and it was immediately apparent when the correct combination was found. Put everything back together and now it purrs like a kitten at 650 RPM... Hope this Helps
