I noticed the mower smelled a little like gas this morning, and the deck had a bit of wetness beneath the carb, but I couldn't see any active leak.
I looked again after running the mower and noticed that the carb was leaking gas at a rate of about a drop/second. I clamped off the fuel line and tried to find out where it was coming from, by performing the following:
1. The Bowl stud was a little loose, so I tightened it and the bowl drain
-----No change in leak-rate when I un-clamped the fuel line
2. The carb gasket plate (between the carb and the air cleaner housing) appeared to be the source of the leak.
2.a. I removed the air cleaner assembly and inspected the gasket plate
-----It looked fine and matched the old one that it replaced
2.b. Figuring I had failed to torque it down properly I was careful to tighten down the entire carb (two nuts), sequentially, 1/4 turn each until tight. The forward nut tightened snugly, as expected. The aft nut seemed to require less torque, even though I had tightened it one flat past where the forward one was fully snug.
-----BIG MISTAKE!
-----Suspecting something was wrong, I attempted to loosen the aft nut and noticed it was wobbling
-----With three flats exposed, it began to back-out the head stud
3. I could not see at the time, but when I tried to slowly work the nut back and forth, the fact that the stud was stripped was apparent...
-----Ah, poop
//
I also removed the idle-adjust screw and popped out the plug yeehaw mentioned. It didn't look bad in there, but I douched it with carb cleaner. The o-ring looked to be in pretty bad shape, but usable for now...
Regardless, with the stripped head stud, this thing is OOC until I find a replacement. Any ideas on where to find new studs? The manual for this model number (12A-18MC056) only shows the whole cylinder head (including the carb studs) as one unit, with no individual part numbers. Looking at newer models of the CC550, the stud is available, part #: 710-04981 (STUD-M6X113)