How to install/orient the throttle valve (p/n 221986). Does it make any difference? This is on a one piece flo jet carburetor (p/n 491590) I have removed the main welch plug and am looking down the throat of the carb. with the choke lever and venturi removed. Does the valve slide into the throttle lever with "X" marked on the valve in the downward or upward direction? It actually seems to work both ways. Please advise.