Been fettling recently (not that the 4rt demands much tho') and I wondered just what purpose the gauze-like metal grill in the air box serves? Is it essential to keep this fitted? I have kept it in place with both the 4rt's that I've had/got, but now wonder just how important it is. I seem to recall one thread saying to take them out and just use the foam filter alone (like in a 315R).

Any views or opinions?

Hi,i believe it is a fire screen,i use the jitsie filters and was told you did not need it with them as they have it as part of the filter,they seem to breath better and you notice less engine brake.