If the battery has been sitting for a length of time in a discharged state, it may not be a 'healthy' battery .
If it is a serviceable type, one you can add water to, check the fluid level, add water to it before charging it .
Did you drain the carb float bowls, or run them dry before storage, if not, you need to remove both of the bowls and clean out whatever may be in there, that doesn't look like fuel .
Other than that, you should be in good shape .