I have a 1991 Super Glide Low Rider Custom FXLR. I had a 5.2 Gallon Gas Tank Constructed out of a Old FLH 5.2 gallon Tank. The Fabricators were not worth a flip so they Jerry Rigged it and decided to make it easy on themselves, so they left out the Tank Vent.
So Yours and My problem is the Vented Gas Cap we are using. This Cap is only for Fuel Injected Bikes where the Tank is completely Closed and it has a Fuel Pump. That Cap only lets a very Small amount of Air in, not enough for Gravity to do the Job as our Models were designed. This Tank Vacuum Causes my New Screamin' Eagle Big Bore Carb to Dump Gas out the Carb Over Flow Tube because the Vacuum is great this Cap Creates. Many People who have Older Bike with CV Carbs have complained to Harley but so far they refuse to address this Issue.
To Fix it, I could ride down the Road with the Gas Cap Loose a Few Miles after Fillup's. But I'll get another Tank made Correctly.
