FWIW... some observations / tests. Fresh 91 octane fuel in a clean glass jar with a nail hole in the screw on top to replicate a float bowl, guess what... after 25-30 days, 2/3 of the fuel had evaporated. If a sled sits for a long period of time I'm sure the float bowls would react the same making it difficult to start. Tested - my 2002 SRX has electric start added. Sled COMPLETELY dry of fuel at beginning of season, add 20 L (approx 1/2 tank), fuel lines from pump removed into a container, crank motor over and guess what - NOT A DROP came out of the lines. Filled float bowls with fuel manually (lines still off), crank motor over, full enrichener, sled fires instantly and after maybe 3 seconds fuel comes out of lines. I'm starting to believe that we simply can't create a strong enough vacuum signal (spin motor quick enough) to draw fuel from the tank to pump when the system is "dry", even using electric start. For my sled, once bowls are full of fuel, sled fires instantly cold / hot / whatever... everything set to factory spec., ZERO issues...
X2 - I've had pilot plugging (waxing) in as little as three weeks of evaporation (sled not started). The oil and contaminates in the bowl become consentrated and isn't very combustable until deluded with fuel.
Different opinions regarding summer storage with/without fuel in the tank. I used to drain the tank and carbs completely but I've changed over the years and currently leave in the tank the gallon or so of fuel/ATF used for fogging in the spring. I add a couple gallons in the fall when prepping for the season then top it off with fresh 93 BEFORE any riding. If I summer stored with a full tank I would drain and fill with fresh 93 or add at least a half bottle of octane booster to the stored fuel before riding.
I'm probably over cautious, but I use a wood stove and just don't like to store or handle fuel in my barn or sled shed.
When getting fuel at the station I start the premium pump and put a couple gallons in my truck before putting the nozzle in my sled or jerry cans. Still doesn't ensure the fuel coming out of the underground tank is fresh premium but at least I'm not getting a hose and pump full of 87. I also get behind my high octane buds when lining at the pump when riding ;>)
Having a bottle of octane booster, well wrapped in the trunk of a sled that requires premium provides cheap insurance and peace of mind when fueling at those out of the way filling stations. When in dought, I use a half can to a full tank.
I performing the following after summer storage:
1- Clean the carbs (amongst many other preseason stuff)
2- Push outside and add fresh fuel
3- Teaspoon of PREMIX into the cylinders (I use fuel from my chainsaw gas can)
4- Tug hard once with full choke
5- Off choke then blip half choke until it'll idle on it's own
If it starts but stalls, repeat steps 3/4/5 - maybe even a third time, tops.
If it doesn't start, you have other issues (i.e. check the key and kill switch then for spark at the plugs).
