Gremlin in my charging system

I've got a 77 kz650 b1 with a bit of a gremlin in the charging system. Once we got the carbs figured out (thanks to all the awesome feedback and info on this forum!!!) she ran like a top unless you turned the headlights on, then she died out. That was about 2 weeks ago. I've been starting her up and letting her idle w/ the lights off here and there so she didn't get gummed up or anything over that timeframe. Went out to do it today and just for giggles I clicked the light switch on to see if it still happened, and she kept on idling like a champ. After about 5 minutes of this I jumped on for about a 20 minute ride (keeping her close to home just incase she died on me), kept the high beam on and rode through low and middle rpms without any issues. Once I parked her in the garage I grabbed my multimeter to check the voltage at the battery and w/ the lights off it read 11.4, when I clicked the lights on it dropped to 10.6 volts.
I'm just baffled as to why all of a sudden it would run w/ the lights on when it wouldn't before...I've got a new old stock stator coming UPS (should be here in a couple days) and I'm going to replace that once it comes in, but I'm wondering now if that was even my issue. Anyone out there ever experienced this or heard of it? Any ideas as to what may have caused the gremlin? Or should I just consider myself lucky that the little snot moved out? Thanks in advance for the help everyone!!!!

I had a lot of issues with charging and running before, found the problem to be bad wires in the handle bars, a 650 runs the wires through the bars, getting the wires out and repair the bad spots made a big improvement

Hand controls and wiring harness have all been replaced (and thoroughly checked to make sure there were no bad spots). The harness that was on her when I got her was hacked to oblivion and the hand controls were FUBAR'D! So, I'm pretty sure it's not any wiring from the controls or harness.....stupid gremlins....

Stupid gremlin.....I got lulled into complacency by the seemingly functioning charging system and took her out to fill the gas tank. Made it to the station about 4 miles from the house, topped her off, went to start up and ride off and the electric start wouldn't turn, and she was REALLY hard to kick over w/ the kick starter. I can only assume at this point that it's something w/ my stator or other components in the charging system. I'll post any updates after the stator gets here and I get it slapped in.

I have owned my '77 KZ650C1 since new - over 29 years. You have perfectly described the symptoms I have experienced everytime my battery needs to be replaced. If your battery is more than a year or two old, replace it first before you pull apart any electrical stuff. I have found the electrical system on the 650 to be very reliable (except an occasional loose connector). Ed

77 KZ650B1 here also. Exact same problem. Mine's intermittent, so I'm doubting it's the alternator. My Regulator/rectifier is brand new, upgraded to electronic type. My battery's a Walmart one, about a year old, so I'm gonna check that first.
Mine ran excellent/like new for the last 2 days. Then yesterday, as soon as I switched on the headlight, the volts dropped to 10. Not sure what the problem is yet, hafta check it after vacation. But I'll say this; it has caused a lot of heartache and unnecessary parts replacement for me, and for alot of others, I'm sure. MAY I HIGHLY RECOMMEND THIS?: Do yourself a big favor, and get one of these tiny yet accurate LED voltage gauges. Mine tells me, as I'm riding, the minute something goes wrong. I can simply switch off the headlight and continue riding without a problem. It's the best single accessory I've bought yet. It's about 40 bucks, available at DennisKirk, and lotsa local bike shops also carry them: Kuryakyn L.E.D. Battery Gauge # 604219, available in chrome or black
denniskirk.com/jsp/product_catalog/Produ...81&leafCatId=&mmyId=

My kz did that to me today also. It had to be jumpstarted and the battery is only 3weeks old. It ran well after the jump, but its still going to the shop. Keep me posted.

I pulled the battery out; one cell was low, one was about half empty. I topped all of them off with distilled water and put it on the charger...then put it back on the bike. After starting it, volts were in the yellow range (on my LED gauge)10V. With the headlight on it went into the red. Worse than before I "fixed" it. Hydrometer readings were all very low. So I know it's time for a new one. I'll probably go with a maint-free type, not sure which one yet(I only found 2 for my 650):
www.bikebatts.com/product_info.php/cPath...2_355/products_id/26 OR www.bikebatts.com/product_info.php/cPath...2_355/products_id/77
Going on vacation for a coupla days, will check in here when I get back
Lemme know how you make out..

After researching, I see the maint-free batteries offer no more warranty than the standard type, and at twice the price. I just went and got a NAPA battery for $38 Total, gonna see how long that one lasts.(The Walmart one lasted one year and one week).