Our snowblower is an older model Arien, I'm unaware of the motor type because it is not the original. It has to be started using a jumper cable, and looks as if it has seen better days. My dad, the owner, has been taking good care of it, and it was working fine yesterday, but today, when he tried to start it up, it would not catch and it started backfiring from the carberator, upon inspection we discovered it was flooded with gas. We let it set and hopefully drain, but upon starting it back up, with the gas cutoff, it once again flooded and started backfiring again from the same area. Please, someone help us.

Someone left gas in it for a few months without stabilizer.

Diaphram carb? Take apart and clean.

Hi,
Could be a dirty carb, but my guess is the intake valve is stuck open.
From my experience(35+ years) only two things routinely cause your situation - ignition timing and intake valve not sealing properly.
To explain, the gas and air are mixed in the carb, pass through the intake valve into the combustion chamber, are sealed in there and are ignited to produce power.
The only obvious ways that ignition will occur in the carb is for the ignition to arrive at the wrong time or the intake valve to not fully close, leaving an open path.
That said, do you have compression, does there seem to be enough resistance when the engine is spun over? There will be some just from moving the internal parts and anything external. Was the engine running with no mishaps to stop it before it was stored the last time?
Should I prove correct, the "easy" way to free the valve is to remove the spark plug and look inside through the hole with a flashlight at the valve. Pulling the starter through you will see little or no movement of the intake valve. Spray some lubricant at the valve in a way to get it to run down the stem and carefully tap or pry the valve down through the spark plug hole(care is needed so as not to damage the threads for the plug!) This will have to be repeated numerous times while turning the engine over between applications of lubricant. After several times the valve should shut enough to crank the engine. Run at full speed until hot to try to finish cleaning the valve.
If this is not the problem, suspaect ignition and the fact that the machine was put up in a non-running condition because of some mishap and the flywheel key would be suspect since that would make the ignitiion arrive at the wrong time.
Peace,
Clarke