Leaving the gas shut-off valve open

[panoply]

Every once in awhile I forget to shut the gas off when I park our stock 59 pan. I'm sure it opens and shuts for a reason, what bad things can happen by leaving it open over night?

[Snake33]

I don't think it is a huge problem, unless your carb float isn't set right or working properly, in that case you will get gas leaking all over the place. This will make a mess on the bike and/or floor and cost you money in the form of gas.

[Cotten]

Overnight ain't so bad, but...
Even the best of floatvalves will seep. Just like oilpump checkvalves. Neither are ever absolute.
Since OHV carbs point upward when the bike is on the kickstand, gas can drip through the manifold and past the intake valves into the combustion chamber, robbing the rings of start-up lube. As more gas drips in, it passes the rings and thins/pollutes the oil. Not good.
Original petcocks are a bitch to seal tightly. My wife uses pliers on hers. (Mine has a inline valve added.)
If the machine is expected to sit idle for extended periods, sit the bike up straight, or drain the gas.

[King]

My tank shut off packed it in years ago and as Cotten said no matter what carb I was using sooner or later the float valve would leak. About ten years ago I started using an in line shut off. The first ones were brass and looked cool but in about six months they would gum up, become hard to turn, and then start leaking. I now have one made of some trick plastic that I got at the John Deere store for about five bucks and it works great. it sits in a section of rubber line just below the Bendix.

Have a great weekend.

King