Generator Out Put

I have 2.5KV chines generator running well but not give power /out put until i remove the air filter and open choke full.

After running few seconds without air filter it start giving out put. I have to do it every time i need it. Start, take of the air filter, and place it back after it starts generating power/out out.

any idea about causes?
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Certainly the choke should be full open during operation.

What does the manufacturer say about the problem?