Morgans wrote:

Add me to the list. I recently got out my 6 1/2 HP Briggs overhead valve
push mower, and it would not start when I put fresh gas in.

I took the carb apart, and it is complete trash. I don't even think
cleaning it would help. It will require a new carb.

It has been about 1 1/2 years since I last used it. It is JUNK , now.

Would av gas be any better? I don't know. I do believe that you had better
keep mogas less than a year in your machines, though.

I've never had problems letting gas sit through one winter (about 5-6
months where I live), but I now use Stabil just to be on the safe side.
I had a Kawasaki KH400 that I let sit for 1.5 years once. That was a
HUGE mistake. The bike wouldn't start so I pulled the three carbs. The
float bowls were covered with a green slime that looked like algae.

I did some resarch at the time and learned that certain things actually
do live and grow in gasoline. I was finally able to clean the carbs
enough to get them working, but it took many hours of mechanical
scrubbing and poking open of fine orifices in the carbs. The green
slime was completely immune to carb cleaners, alcohol, acetone, etc. I
tried every common solvent and cleaner I had and nothing would touch
whatever that stuff was.

Matt