So, i changed the plugs on my new to me motor earlier from a set of ones that the guy said were fouled...put the water muff on, and tried cranking...the motor would crank, and start with me pushing in on the key and the neutral idle all the way up, but as soon as I let go, the motor would shut off. We ended up speaking to a buddy of my dad, and he fooled with this valve on the top back side of the motor that turns (its a red triangle looking valve) and looks like it has fuel lines and electrical wires....when he turned this, the motor fired right up and idled on its own....when he would turn it back the other way, the motor would die. What is this valve? it has a picture next to it showing an arrowing turning it, but im not sure what this does?? thoughts??