I live in Ontario and we have been getting temperatures ranging from -30 Celsius to -40 Celsius. I have generator in heated building when I'm not using it. I haven't had any problems with it all winter. I regularly change spark plug and oil. When I first bring it outside I can run big loads from my house on it fine like my keurig in eco mode or jet pump in high mode. Everything works fine for the first 10 minutes or so. Then after that period of 10 minutes the generator has difficulty powering big loads and sometimes shuts down generator. It can still run 30-50 amps loads still but not big loads without difficulty or shutting down. The crankcase breather hose has ice forming in it at the end of the tube going into the air box in that 10 minute period. Does this cause the generator to have difficulty running big loads. Is the ice forming in that breather hose the problem? If it is the problem is there any way of fixing other than waiting for warmer weather. I would usually contact the Yamaha dealership in my town but its closed. The appliances that require more starting power(jet pump,keurig coffee) make the generator have difficulty or can even shut it down. But once those big appliances start they run normal without difficulty. It just when they kick on. Could the carburetor be dirty (not surging or sputtering though)?
" temperatures ranging from -30 Celsius to -40 Celsius "
Yikes!! You certainly have a carb icing issue. Maybe even a hard frozen inverter. Try redirecting heated air output from the Genny to the cooling air inlet side using a few feet of flexible clothes dryer exhaust ducting, substantially Duct taping it into place. At -30C there is NO DANGER of overheating the engine or inverter. Temps that cold are over-cooling the engine oil too. Please report back after the mod.
I brought it to my Yamaha dealership to repair it. It wasn't surging or sputtering. It had trouble starting appliances that required lots of starting power. I would have had it in an enclosure but it never stays this brutal cold out. I always have it the house when I'm not using it. It warmed up a lot the other day but It is still acting the same (having difficulty jumping to a higher rpm when big appliances are plugged in). It's probably a carburetor issue like you said. Would rerouting the exhaust to the air intake harm it ?