Ok, the part outlined in red is your choke, you have an electric choke, and your carb appears to be a Rochester E4ME
http://www.tocmp.com/manuals/Carbs/R...age064_jpg.htm
http://www.partschoice.com/carbs/tec...jet-index.html
The part outlined in blue is your choke pulloff, this holds the choke upen while the engine is cold. To see if it is working properly, push the lever coming out of the end of it in, and hold it in, then take a pair of needle nose pliers and pinch the vacuum tube that is attached to the choke pulloff, it is outlined in yellow. Then, let go of the lever and see if it stays in the pushed in, if it does not the choke pull offs seal is bad, and the whole part will need to be replaced.
