1942 WLA Bobber 

Good question. For this year, the tank on the left is gas, the tank on the right is oil. The left tank is much larger, and goes under the frame to the right side, and the right side oil tank is smaller with an oil dipstick inside it. The right cap says "OIL" on it too.

@@southhillcustoms oh ok i always liked that look never known that tho thank you

Also, FYI, In later years it's just two gas tanks.