I have a 3.5 B&S motor with pulsa jet carby in a Rover 45 mower which appears to be missing a spring. I found a picture of the same setup as mine elsewhere in these forums and have captured a section of it to show the one I mean. My engine runs but not quite as sweetly as I think it should; could this spring be the culprit? numbers for my engine are 91202 0123 01 930920 Can someone help with a part number and source for this spring please?