My "new" 9N starts and runs, but after it's warm, it bogs down and quits easily.  I think part of the problem is with the choke, which flops open and shut VERY easily.  It looks like there should be a grommet or clip where it goes through the instrument panel, or possibly some kind of retainer between the instrument panel and the carburetor.  Never having seen a tractor up close before, I'm just guessing (dunno squat about tractors, but when I was much younger I overhauled several different car engines & like that).  Either way, automotive chokes I've worked with have been held better than this one is. 

Also, I wonder if I might have crud in the fuel lines.  Everything looks OK, but I've seen a reference to "riser" tubes in the gas tank.  How does one get to these little buggers?

Thanks in advance.