Disconnect the battery and remove the battery from the bike. Wash battery compartment with a solution of warm water and some baking soda, do same for the battery. Reason is that salt will build up in this small space and bridge the battery terminals and the salt will discharge the battery. If you live where they put road salt down in the winter, or take a trip where they do you can pick up the salt and then the battery problems start. This one gets missed a lot and people spend a small fortune hunting down the problem.
