'07 Wolverine 350 won't idle
 

It ran last at the end of Aug, but had a very sloppy idle until it warmed up. Now I can't get it to idle long enough to warm up. It will start and run for a few seconds, but it's barely alive. Fuel is from August and has SeaFoam in it as a stabilizer. I pulled the plug and it looks fine. Any thoughts?