No-one else has responded so I'll have a crack at it. But it will be assuming that the pcv system in your B280 is similar to a B28 (Haynes says it is, but that doesn't neccessarily mean it is so).
There should be a plastic oil filler cap about 3" long. There should also be one or two vent pipes coming from the cap: one to the air inlet tubing between the throttle body and the the air filter, and possibly another smaller one going to a nipple somewhere. On the B28 the mesh inside the oil filler neck which you spoke about is retained inside the filler cap. It is held there by a perforated plastic disc which clips into the lower end of the cap.

Don't bother trying to clean the mesh. Buy a stainless steel kitchen pot scourer from your local supermarket. Get a big one. Gently push it into the filler cap. Trim off any surplus. Replace the perforated disc to keep it in place. Again, I'm assuming your B280 has a similar system to a B28.