My saw was a gift, last serviced in 1991. Air filter looks like it's covered with velour, but suspect it is what is known as floccing. When I rub my finger gently over the surface it seems to powder off, making me thing that it has deteriorated...do I need to get a new filter, and where do I find one? Are generic filters available with same shape (rather like the Ketchup Cups at fast food places). I'd appreciate any help I can get for this little saw....Thanks.