I have a 1968 KT120 Suzuki that had the same problem. I had also cleaned the carb several times before and even soaked the carb over night in a gallon bucket of carb cleaner. I was going to get rid of the bike due to it being a pain in the butt. Well one day I had nothing to do I took the carb a part again and noticed the small jet (not main jet) was completely blocked. I don't know how I missed it the first 3 times, but I did. Now this 1968 starts on one kick everytime and I'm going to keep the bike.