If you used "ReaLemon" juice that does have preservatives (two kinds of sulfites.) I use this stuff in the skeeter pee recipe on this site and you have to make a double starter and let the water/sugar/juice mixture sit for a day or two to let the preservatives off gas.
Did the lemon soda ever get going?
Primary: Ginger Beer
Kegged: UpstateMike's Caramel Apple Cider, Strawberry Graff
Bottled: Edwort's Apfelwein, Brandon O's Graff, More Graff, Spiced Graff, Ginger Beer
Up Next: Graham's English Cider