11.8v is way too low. Did you charge the battery before installing ? Before diving into the bike (which presumably started OK before) I'd double check the battery voltage off the bike and then charge it and then leave for a day or two before checking again that it's holding a decent resting charge at around 12.6v Checking the date code on the battery could show if it's been sitting a while on a shelf. If a new recently charged battery won't hold a resting charge of around 12.6 v then it could be faulty.
