Does it matter whether the oil filter is horizontal or vertical?

 

Some oil filters have a designed back flow preventer in them, others don't.
Most oil filters are mounted vertical for a cleaner oil change. Harley has oil filters mounted vertical as well as horizontal depending on the bike so I would think your O.K. both ways, I'm just not positive!
hatch.

 

No difference in performance of the filter, no matter what angle.

 

thanks guys, the bolt holding my filter up (90 fxrs-sp) came loose, left the filter almost dragging on the ground. Going to fab a bracket to make it for a few more rides then do it right over winter. Was concerned about possible check valves.

 

Mine did that a few years ago! It is enough to clean things up and dab some blue thread locker on the guilty screw, to bolt things back together again.