A few days ago I went into the shed turned on the key listened to the start up hum, but at the same time there seemed to be hissing sound with fluid mixed in coming from under tank. Now the fuel was down to say 1/2 gallon in the tank and the shed was real hot as its summer here. So I turned off key then back on 2 more times,so in total it made that same sound 3 times and promptly stopped and has not done it again. But here's the thing, i went for a 120 mile ride and when i got home this weird streak appeared on the left side front of tank on the cast frame. It wont polish off and seems to etched into the casting. It stars on top of the frame then goes down the left face of the frame. Have had tank off and no immediate problem was seen I also have had into workshop and they found no problem with the bike. it runs about 20mm out from tanks and follows the shape of the tank perfectly. Anyone seen this on there scout?