A note on storing gas. I worked in a power sports shop for many years, so cleaning and rebuilding fuel systems was something I did daily.
Modern gas is not like gas of 20 years ago. A generator/motorcycle/jet ski sitting since the 1990s, would have a little buildup of deposits in the carb, but it was an easy clean and get it back up and running.
The same engine sitting for 3 years, would have a complete mess in the carb due to the newer fuels. Just complete green tar like mess. It was a real pain to clean.
On modern fuels, how long you could let the fuel sit in engine, with gas in the carburetor depends on the type of fuel used, and the size of the carburetor. Smaller carburetors like on small generators, weed whackers, small dirt bikes, would plug up in about 3 months to the point they would run poorly, or not at all. Fuel stabilizers added to the tank would tend to extend that out to maybe 6 months.
Bigger carburetors would hold out until the 6 month mark or so, before the varnish would build up too much and the fuel would adsorb too much moisture. Basic older engine designs with low compression might do OK with this. Adding a bunch of SeaForm to several tanks of gas could help remove the deposits, assuming one of the passage ways of the carb is not fully plugged up. High compression engines like 250/450cc dirt bikes did not like this old fuel at all and a full rebuild was needed.
None ethanol fules like TrueFuel/Avgas/racing fules, did much better. The gas did not start to go bad in the tank until about the 2 year mark. But once it did go bad, it went really bad. Thick tar like goop in everything. It was an extra $100 charge to clean anything that had been sitting with racing fuel in it past the 2 year mark.
Now out of that profession, and not ever wanting to clean a carburetor again, I now take the following actions.
What I do for my gas generators to "summerize" is empty all fuel out of it, including draining and removing the float bowl. I let it air out for several hours. I then fill the float bowl up with ATF and reinstall, along with adding some ATF to the tank and swishing it around. The ATF keeps the seals in the carb and other rubber parts lubricated along with absorbing fuel and displacing dust and insects. When I need to use it, I remove the float bowl drain screw, train out the ATF, fill the tank with fuel, and it starts right up.
For weed whackers and small engines, when I am done for the week, I drain the normal fuel out of them, and fill with TrueFuel, then let idle for a few minutes to flush out any normal fuel. I then drain the TrueFuel back into the can, and let it run until it's out of fuel. Then leave the gas cap loose while it's in storage.
Since doing this, I have had zero fuel related issues. No carb cleaning, nothing. Stuff just works now.
