Don T, Ken I: There is NO "rear seat". There is a rear seal which is what gets bumped into. When that wears out/dies of old age, there is nothing to hold the cutoff/on screw in place and it vibrates out. The last time I tracked that part down, a replacement cost just a bit more than a whole new fuel bowl assembly from Kohler! Dumb-de-Dumb-Dumb!!...However, B&S makes a replacement, complete, fuel bowl assembly, which is a bit shinier than the original, but otherwise is pretty much the same, a direct swap out, inexpensive and easily available. That is usually what I do an old one starts leaking...
Myron B
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