If you have not used your EF2800i in some time it is very likely the carb is partially blocked.
I have included a picture to help you with the tear down and reassembly.
It is recomended that you remove the carb assembly and disassemble completely,including removal of the jets (#13,#14) and main nozzel (#4) clean with combustion chamber cleaner part #ACC110008200 and blow out the jets. Hold them up to the light to check for clear through with no obstuctions.Upon reassembly you will need to reset the float height (16mm) then reinstall carb and have a go !
In the future you should always use Fuel stabilizer part #ACC110008000 on a regular basis as you never know how long it be before you have to use the generator agian. Also when you know you are not going to use it for some time, you should turn the fuel off and run the carb dry, store it with no fuel in it.
For your own information.
Fuel is only good for about 90 days before starting to go stale.
After 6 months it will start to sludge up, plugging small jets,etc. www.YamahaGenuineParts.com