guys i am here for some help with a honda foreman 400fw. i just had it bored .50. Put it all back together, set the valves. heres the scenario.....

it will start after holding hand over carb intake, then will sit there and idle very high, like say 1/4 throttle on a normal honda engine. will run like this and excelerate smoothly to the top of the throttle, but when I let off it stays idling high for about 45 seconds and dies, when it does die, i try to give it gas but it sputters out and dies. I cleaned the carb well atleast the bottom of end, all the jets looked good. Any ideas??????????!!!!!!!!!!???/
Thanks in Advance,
jay

Things i checked....gas cap vent, cleaned petcock...wasnt to bad