can any body tell me why,when i start my sy250 from cold ,using the choke it starts second kick,choke back in and the bike runs fine.then when i stop the bike and try to restart the bike when warmed up ,it still will not kick over unless i use the choke.can anybody tell me why it will not start unless i use the choke even when warmed up .thanks.

make sure when its warm you give her some throttle when starting, if you are already doing this you might want to give the carb a good claen and check the jets,also check all carb fixings are tight and not leaking air

Sounds like its lean on the pilot/air screw.

Blocked or incorrect pilot jet.