Hello dineshdeshmuk,
there are many reasons, why your motor don't start. I can only tell you my own experience with my generator.
1.) Look, if their is enough gasoline in the gas tank and look if the fuel tap is open, and also enough motor oil. This is not a joking question, because the gasoline will vaporized. I don't use the generator soo much, and so I forgot to open the fuel tap.
2.) Look for the spark plug. Is it black and dirty or is it wet. If it is black and dirty you must clean it really. The black dirt is coal and makes a short circuit for the ignition voltage. If you can not clean it, change it.
Check the spark plug. Do it like this: Connect the ignitions cable to the spark plug and hold it to crankcase. the try to start the motor and look for the spark. You must see it good. Take care of electric shocks!
If it is wet, the motor get too much gasoline. Clean and dry the spark plug. Test the spark plug, like I say before. Put the spark plug into the motor.
3.) If the spark plug was wet, look here, else goto #4.)
There is too much gasoline in the carburetor. Close the fuel tap and try to start the motor. Short time before all gasoline in the carburetor is use, you feel the motor want to start. Then look again for the spark plug, and if necessary dry and clean it again. Now open the fuel tap again. Try to start again.
4.) Now look, if the carburetor gets gasoline. Sometimes it can be, that dirt is comming into the gasoline line. If it is clean, the carburetor has a fold. Here I canot give a advice, because I have no experience. It's better to ask a motor specialist.
I think, the air filter will not be the problem. If it is dirty the motor will not bring full power. It's the same, when you have too less air to breathe. 8-O
I hope it hlp to start the motor again
Best regards
Rainer