I took a new AN650 filter over to an auto parts store and fit it to a wrench cap in the store.
The auto parts store filter cap was only a few dollars compared to
Suzuki's $15+ price.
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My AN400's oil cartridge filter cover won't leak as long as I clean the mating surfaces
and dab a film of oil onto the 'O' ring before placing it back down into
the recessed channel at the cover.
An indication that the cover "O' ring is not completely sealing is that after
the first few rides after having done the oil change, the housing around the
seal will mist with small amounts of oil. This may stop itself.
Remember to tighten the AN400 filter cover only enough to keep the bolts
on as the oil seal is mostly done by 'O' ring contact. The recessed channel
for the 'O' ring prevents compression damage if the cover bolts are
over torqued.
I keep an extra small 'O' ring to compare with the cartridge shaft one
each time I change the oil. As long as the small 'O' ring doesn't compress
or crack, I continue to use the old one.
See this post>
http://burgmanusa.com/forums/viewtopic.php?t=495
It has pictures and part numbers for doing AN400 oil changes.