My 98' big bear 350 4x4 runs poorly when the engine is cold. I mean it can be 80 degrees outside and if the motor hasn't been run and you start it and try to take off it will stumble and stall. Once it warms up it runs perfectly. When the weather is below freezing it has to run with the choke on for at least ten minutes then with no choke for ten minutes before I try to ride it. I don't think it should have to idle this long before i ride it? Any thoughts what could be causing this? Thanks Bob