2 strokes are bad at starting full stop. Forget air filter. Leave it out. Get a new plug first. 2 strokes eat plugs. Right....with plug out, turn over bike for a few seconds on full throttle. Then hit carb at the bottom of float chamber with screw driver end (not tip) just in case float is sticking. Warm plug as before. Put in plug plus ht lead this time Make sure kill switch is on and ignition Dont start with starter, bump it off as fast as you can in second gear. Start with no throttle then full then none etc, doing this quickly. Does it start. If yes, did it start on small throttle or full? If it doesnt start. Take plug out, connect back to ht lead. Place the end of the plug on top of engine. Now turn everything on and turn it over. Is the spark strong and what colour is it. I don't know whats your bike is like, but its either intake or coil end. After this you need carb stripping and checking over by a good mate who will show you how its done. If you lived close I would do if for you