air box cover not tightening up>> fucked thread

out of the 3 screws that holds my airbox cover on only one tightens up properly another one will tighten up but not as tight as it should be and the other one doesnt really tighten up at all. i have tried fitting a slightly larger/longer screw but it hasnt really had an affect. someone has suggested self tapping screws? would this work or could there be other solutions? cheers.

 

ok mate was thinking this. if i lift the cover off and try screwing in the screws with the cover off they only seem to tighten up when the screw is nearly all the way in. the screw seems pretty loose when im tightening it up and i can push it in like nearly all the way in before having to screw it in to get it further inside. (if that makes any sense)

 

just gnna try self tapping screws. cheers.