Well, took my old tank of today because im in the process of painting a new one. I took the fuel filter off to see if i could unscrew that cap to see if i could blow it out or anything (nope). When doing this i discovered an arrow on the filter indicating gas flow and it turns out that the PO had the thing backwards. Im obviously going to replace the filter now but wondered if anyone knows how those filters work. It looks like a solid porous material inside buts obvious that it needs to be mounted in a specific direction. Just curious, anyone have an answer?

 

the direction isn't critical, it will just clog faster if installed in reverse. filters are made of different matierial. some are paper filters, serries of mesh screen, and i've seen some that look almost like a real porous type of metal.
install with arrow in direction of gas flow.

 

If you have not got a replacement filter yet, I found a good deal on e-Bay there $3.95 free shipping for a Emgo brand OEM replacement from TASClassicmotorsports.
I installed one on my 87 600 Hurricane and it looks just like the OEM one witch goes for $14 at a Honda dealer.