Smallest Battery I can get for 78 KZ650?

Look into Shorai Batteries, Lithiun Ion, super lightweight and small.

I'm running a 1.2ah sealed lead acid (agm) battery for an exit sign/battery backup. I have an 82 750 twin, kick only, head, tail and brake light only. So far so good and at $15 shipped off of ebay I won;t be pissed if it only lasts one season. I've read on other forums about using a .8ah on xs 650's. There about the size of a deck of cards.

That 1.2ah looks pretty cool, especially for the price. What do you mean as an exit sign/battery backup? And can you still have the lights on and kick start it?