I would definitely go looking inside things for sand - did it on mine, in fact, even though it was apparently (and actually) clean as a whistle. Unmounting the air filter and having a good look at its insides and plumbing to the engine would seem a reasonable thing to do.
Likewise, pop the Dzuses on the control cubicle, flip the panel down and have a careful look inside for critter nests or sand. You want to do this anyway to check for things like oozing potting, cooked or frayed wires, or obviously damaged components. Mine was great, but it did benefit from a little screw tightening on some of the terminals.
As I think about how these machines work, it would seem that the cooling fan on the front of the engine might be a good sand indicator - it's a big squirrel cage blower and any significant amount of sand going over the vanes while the engine was running would probably sandblast them pretty efficiently. Can one of you folks with a genset that definitely came from the sandbox have a look at this to confirm or deny?
Another thing to be cautious of is fluids. My set was very carefully defueled and deoiled before it was sold. Nothing in the crankcase, nothing (but condensed water) in the fuel tank, and no filters anywhere. The good news was that nothing had turned to gunge in the fuel system. The bad news was that I could have put oil in the crankcase and started the set without oil or fuel filtration if I hadn't methodically looked at everything before attempting a start.
Resist temptation, be methodical, and, when in doubt, refer to the -12 TM for both what is normal and what SOP is, as it is not always intuitive.
