Is that stuff kind of thick like gear oil?Adding my 2 cents worth.
I doubt that the batter is the culprit here. Probably fuel supply\
If you do go the route of fuel additive, let me recommend the regular use of LUCAS fuel additive. I use it in all my vehicles constantly. On my antique BMW which the carbs weren't that good, after cleaning the system, I started using Lucas, and from then on, the fuel system stayed spotless! Never had the problem again!
Since it mixes at a 400:1 ratio, it goes a long ways. I purchase it in the gallon jug, which lasts a looooong time on all my vehicles, 2 cars, 1 riding mower, and one motorcycle.