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When I reconnected my tank I had an overflow problem. The bike was parked in the sun on a hot day and when I came out at lunch there was a pool of gas on the ground and gas dripping from the bike. The cap was vented (but the vented caps let air in - not out). I removed the tank to check it out. The problem was a small piece of trash in the rubber vent tube. Once the tube was cleaned out it performed as it should. Lesson learned.
A small, flat piece of metal bent and mounted around the battery tray can help hold your solo bag in place and solve the inevitable sagging. I JB Welded a bolt at the point I wanted it to secure the bag. I made a hole in the bag and used a wing nut to secure it. Stays tight against the frame.
I made a cardboard mockup for size and fit and then used 3/32 inch thick, 1 1/2 inch wide metal to make the bracket. Painted it black and mounted it. Can't even thell it's there.