Anyone who has changed the oil filter on a KQ450 probably shares my frustration. There just isn't enough room around the filter to use either strap or cup-type wrenches. I stumbled upon the K&N oil filter which has a 17mm nut built onto the end of the filter. Turn the nut and the filter turns with it. A 17mm box end wrench adds no length to the filter/wrench combo, so you have room to maneuver. I highly recommend a stubby wrench. If you don't have a 17mm box end wrench, 11/16 will work.

The part number for the filter is KN138. They are more expensive than Fram but probably are better filters and the ease of changing filters is worth the price for KQ450 owners.

Agreed, it is a very poor design.,

Thx for the info.
I changed oil last weekend and had to resort to the tried and true (but messy) method of hammering a long screwdriver thru the filter to twist it off.

I'm not familiar with the location of the filter on the 450, but on my Vinson, I use a set of oil filter pliers. I still have to use short strokes, but it works good. I just have trouble taking all the side panels off.