I'll go along with the crap trap filters too but be aware they only fit one way because they use two different sized meshes as the photo below shows. Rubbish can get into the fuel from lots of different places like through the muffler pressure line or from new clunk tanks that sometimes have a very fine fuzz of plastic fibres from the moulding process. A couple of dollars for a filter is very good insurance for that multi hundred dollar model and engine. For the engine I always use the [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LX9160]Bru Line[/link] fine filter which also helps keep the outside of the engine clean by trapping any fuel that might spit back out of the carb.