I run one, probably extraneous. I know there is a filter screen in the petcock but I spliced one between the tank and carbs just as a backup. There was a bit of rust in my tank and I didn't want to risk blocking anything in the carbs. The previous owner had something in there too so I just changed it out. My RS has NO fuel filter other than the petcock screen. It also has an alloy tank so no rust issue.