Scooter sat for a year; wouldn't start; replaced battery. filled with gas. cleaned spark plug. won't start. Help

Check the spark plug. My truck did the same thing and it was because the spark plug had completely been removed.

Pull the carberator off and clean it out at least drop the float bowl clean out make sure float and needle and seat are free if still won't run have to carb all apart

1. Drain the gasoline.
2. Remove the carb bowl(s) and turn on the petcock to drain the fuel in the lines.
3. Clean out the carb bowl(s) and replace.
4. Refill with gasoline, add 1 oz of Seafoam fuel system cleaner (I'm not a sponsor, I just haven't found anything better) to each gallon of gas. This will stabilize your fuel as well as do a great job of cleaning out the carb(s).
5. Try to start it.

If it still won't start, begin the standard troubleshooting procedure by first pulling a spark plug and turning it over to ensure gas is getting to the cylinder. If so, replace the plug, hold the plug wire slightly away from the plug and turn it over to ensure a spark jumps between the wire and plug. If so, it starts getting complicated. Buy a manual for the bike if you don't have one and follow the troubleshooting steps there.

Sounds like the carbs are gummed up from the old gas sitting in them. Remove the carbs, disassemble, clean with a carb cleaner, and reassemble.

HiStart by taking apart the carburetor, replacing the gasket and cleaning it. Then change the spark plug and put fresh gas in. The air filter wouldn't be a bad idea either but you can look at it and tell if you need that. If it doesn't start after that, find someone that can help you troubleshoot.
Hope this works

If the engine is turning, but slow, she may need the battery terminals cleaned, if it has sat for over a year, yes, it may need a new battery. If the engine is turning over and she is not cranking up. Standard rules apply... does she have fuel? does she have spark, does she have compression? First thing is easy, get a can of starting fluid and give her a spray in the air filter area during cranking, if she pops off you have spark, which means no fuel. If it does not try to hit, that means no spark and more trouble shooting will need to be done. If it starts on starting fluid, you may have a bad fuel pump. AS gas turns to gunk as it dries up. And that may have gummed up the pump and filter. Hope this helps FixYa up.

Then you will need to check the switch or stop mechanism. If no problem there, then you will need to replace the ignition module.

First, what color is the fouling on the plug? Obviously the plug will need to be changed. It almost sounds like there is something mixed in with the gas causing the plug to build up. IUf the bike has been sitting for a long time with the same gas in it - have the gas tank emptied(it needs to be taken off the bike and flushed out) and have the carburetor cleaned too.