Trouble starting!

I have a 1981 kz440. Since it's warmed up my bike has actually gotten harder to start. Sometimes it will wear the battery down completly without starting. What could be going on here? I use the choke and that doesn't work. It sounds like it's going to start and then dies right after.

Alright, I think I got it all worked out. I was looking things over and noticed that one of the carb boots (that I bought only a few months ago) was cracked! This is VERY annoying, and if you've had to buy these before you know how expensive they are. Anyway, after cursing the aftermarket dealer/manufacturer of this product to myself, I applied some "plasti-dip" to the crack and that seemed to work for now. Also, tightened up a loose spark plug and charged the battery. She's good to go again! Thanks

Well, the bike is still giving me the same starting problems even though I fixed the boot etc. Any advice?