Hard start and strange idle

Hi, i have a strange problem with my bike. It is Starfire 66cc engine with nt carb(#80 jet, c clip on top slot). When i have to start cold engine, it is very hard,( outside is 35 at celsium, and i need to use chock, or it won`t start))( i need to pedal about 500m). When it is started, at first idle is very low(need to keep engine running with holding throttle). After warm-up it runs really good(top speed 55-60km/h) and it starts really good. The problem started when i insert 80 jet. Where i should search a problem?

At the moment i have ride with it 827km. Compression is still good. I tried to put higher and lower float level. Now it is 23mm measuring from gasket place and it is starting much better, but not as before and runs worse(top speed 45km/h and bogging) .