Chain Aspiration
 

That's what it's called in the parts list. I've been told it's an oil strainer and I should clean it each time I change the oil. It doesn't mention anything in the user manual.

Does anyone else do this or know what I'm talking about?

It's on an 06 450 by the way.

Yes there's a big flanged nut on the side case low down that's made out of soft cheese metal. Behind it you will find an oil screen much like KTM. It doesn't exist on pre-06 and GasGas in their usual Spanish Siesta fog left it off the 2006 parts fiche.

It's in the user manual I have but seems to be overlooked a lot. Maybe that is a good thing as the parts list is/was incorrect for that year (just for a change!). I took mine out and could not get it to seal again. GF managed to get the correct washer in time cos they had the same problem. I managed to seal it with an oversized copper washer and a green o ring used for automotive a/c pipes set inside the washer. Works better than the original so far. I think the filter there instead of the flat sump strainer that is under the sump plate on the earlier models but I am not sure.