Okay, that serial number was NOT part of the affected units with contaminated test fuel from the factory. So no issue there.
However, my records show this serial number
IS in a group of units that were part of
a Safety Recall for a possible fuel tube leak. You did not receive notice of this, since this serial number was never registered with Honda (shows up blank on my database).
It is important you get this unit to a Honda Generator dealer for inspection and possible repair. This issue is a fuel tube clamp may have damaged a fuel tube. The fix (if the tube is okay) is simply to turn the clamp. If the tube is damaged, it will be replaced. It's very important to have a Honda Dealer do this inspection and repair, so the unit can be properly logged into the Honda system and show this unit as having been inspected/repaired. When you take the unit to a dealer, they will also update the records showing you as the registered owner. This allows Honda to contact you if there are service issues in the future. Because this is a full-on Safety Recall,
there is no cost for the repair; you just have to take it to a dealer (and usually can wait on the repairs).
Also related to your serial number, if you can provide proof-of-purchase (with a date) to the dealer at the time of repair, the dealer can also enter that date as the start of the 3-year warranty. Without proof-of-purchase, the warranty start date would be the date the unit was wholesaled, which is 6/14/2012. Not sure when you actually purchased the unit, but it was for sure after that. So try and find some documentation to show the purchase date and get the warranty start date set correctly. FYI, this unit was originally sold by Atwood Ranch & Home; did you buy it there?
Draining gas. Is there instructions for the tank and carburetor draining in the manual? If not I'll need some .
Is there a recommended fuel system cleaner that may or may not be effective in solving the problem?
Yes. The short version is simply to pump out or tip over and drain the tank though the filler neck. Then, loosen the drain screw on the carburetor to get the last few drops out. FYI, the EU2000i has a fuel pump, so you can't just gravity-drain the entire tank. Full instructions in the manual; link to it here:
Honda EU2000i Owner's Manual for s/n 2399031