I've the same troubles with the battery. Mine won't start in the winter months, it's the original one so its about 2 years old. I also have a tender on both my bikes and with a battery thats in good condition they work great but obviously wont resurrect an old and ailing one.
If the battery is low it creates its own problem because all the power goes to the starter it means there's not enough power left for the spark.
The stock battery is only 270 cold cranking amps, those in the know recommend at least 360 CCA especially in areas that experience below freezing temps (we get to minus 8 here).
The cheapest one I've seen so far is over $300 from a battery specialist in Brisbane.