Charging /Starting problems

Thank you in advance for your help!
I have a 1982 KZ1000P. My problem is that something seems to be discharging the battery. I replaced the battery that came with the bike (bought about 2 months ago) and it was good for a few weeks until I needed to recharge it. I am suspecting that it could be the starter motor. This morning I went to start it and after several attempts it just didn't seem to have enough juice. But tonight when I went to start it, it turned right over. I had suspected a few weeks ago (when this same scenario happened) that something was draining it so I checked all wiring with a volt meter and found no problems. I installed a kill switch at the battery just to be safe and use it every time I shut the bike down. Now back to the starter. Sometimes I go to start it and it doesn't start but continues to spin. You can hear a high pitched winding sound then it stops. So tonight when I went to recharge the battery it was at about 95% but not enough to kick it over. Will a bad starter drain the battery just enough where it won't start? I imagine it might... I know that when I put the battery in tomorrow morning (after recharge) it will turn right over, but it seems there is this pattern occurring now. If it is the starter do you happen to know the part number I need to replace? If not what else might it be? HELP!!!
Thank you again, Keith
P.S. This is my first bike and apart from this little annoying problem I love it. I ride everyday to work and can't wait to ride home. I think for a first bike I'm very lucky to have gotten this one.
PSS: I just had one more question: when I down shift the gears seems to make a "clunky" noise especially in 2nd & 1st, Is this normal for this bike?

What you're describing is a classic case of charging system failure. With the battery fully charged and the engine running @ 3500 RPM with the lights on you should see 14.6v~14.9vdc measured across the battery. If this figure is low, check the stator first for continuity and ground. Locate the red wiring plug under the left plastic side cover and unplug it. Checking the wiring harness side of that connection, check the resistance between the three yellow wires. It should be between .6~.8 ohms. An open circuit indicates a burned or an unplugged connection at the stator or connector plug. Next check each yellow wire to ground. All reading should be infinite; there should be no measurable resistance to ground. Any resistance to ground indicates either pinched wires under the chain cover or a shorted stator. Start the motorcycle and let it idle. With the red plug still disconnected, check between the yellow wires with an AC voltmeter. You should see 14~20vac between each leg, depending on the idle speed. What you're looking for is parity; you don't want to see a big difference between phases. Plug the red connector back in and probing through the back of the red plug check the loaded AC voltage on the same yellow wires. With the lights on normally you will find 9~12vac @ idle. The regulator/rectifier check requires a DVM with a diode checking function. Very seldom do they go bad, the only failures I've seen on those have been wires corroded thru by battery acid (it bolts to the bottom of the battery box).

 The starter motor draws somewhere around 60~70amps while cranking if you have an inductive meter or shunt that can check it. If you hear the starter motor spinning and not engaging the engine, or making a banging/ratcheting type noise while cranking, the starter clutch is slipping. If the battery is low and not spinning the starter fast enough the starter clutch will slip also. If the brushes are worn in the starter it may show a higher current draw and usually will crank slower. The typical symptom of bad/worn brushes is a dead spot on the starter. It will crank fine until you stop on the dead spot, then it won't start unless you back the motorcycle up in gear and spin the motor to a different spot on the armature.

 RE: clunking while downshifting. These models vary quite a bit; they're all the same but different. Quite a few of them do clunk while shifting so I would say that it's normal. One thing to check, if the chain is real loose it will hit the center stand stop on the left muffler.