check float level...
It's possible that the engine wants more air because the carb is delivering too much fuel. A high float level can cause too much fuel to be delivered at start and at idle. (A leaking float needle can also keep the float bowl's fuel level too high.)
After starting and idle when the throttle is opened, the mixture must lean out or the engine will not accelerate or it could sputter and die...
If the carb is delivering too much fuel the mixture will continue to be too rich even with air intake at maximum.
Sponge material varys .. closed cell sponge won't pass any air at all.
And the amount of air that genuine air-filter open-cell sponge material passes differs from appliction to appliction. Wash and dry whatever came on the bike. If that doesn't help then the carb needs cleaning and adjusting.
But a general inspection and tune up is called for .. go down the list and check everything.
Cleaning the carb is #1 since symptoms of too little or too much or erratic fuel delivery, like starting problems, are so often due to a dirty carb. But the problem could be elsewhere.