Honda Fourtrax 1986 250

Hello, I just bought a Honda Fourtrax 250 1986. When I bought the ATV the owner had just cleaned the carburetor. I reinstall the carburetor and after the idle was too fast. I adjusted the idle screw but the idle was still too fast. I looked if there was no vaccum leak and nothing was to report. After I check the throttle cable and it was sticking and the throttle cable fall very slowly or he stay upstairs. I then clean that and start the engine. The idle was much better so I wanted to adjust the idle it worked but when I went for a ride the idle came back very high when I put it back to neutral. Do you have ideas Thank you