Preheat oven to 350 degrees. Combine flour, soda, cinnamon and salt in a large bowl. Beat sugars, pumpkin, eggs and oil in another bowl. Combine milk and lemon juice in small bowl and add to sugar mixture. Add flour mixture to sugar mixture slowly , mixing well after each addition. Stir in coconut, carrots and walnuts. Bake in two greased and floured cake pans 30-40 minutes. Frost with cream cheese frosting.