Topic: 1978 KZ650B Electrical Question

[Dr. Frankenstein]

So I finally finished up my CB500 Four and am now turning my attention to my '78 Kawasaki KZ650B. I rebuilt this bike - gosh - six, seven years ago after finding her at an estate sale...rode it for a summer or two, and it was awesome, but Time moves ahead and she has sat for a couple years, so it's time ot get her back on the road.

I have a question about the electrical system - I put a fully charged battery in her this afternoon - 12.57 volts - and she should have spun over, but the headlight and turn signals came on really dimly, and the horn was non-existent, but my Question is, where should I start looking for problems first? The rectifier? Fuses? Coil?

[CycleRanger]

Is it a new battery?
Did you recheck the voltage after trying to start the bike?

[Dr. Frankenstein]

No, it's the one I got for it when I got the bike - it registered 12.53 volts this time after I charged it, but I suppose I should get another one. I was just hoping for enough juice to crank it, or at least trace some problems. Took it back out and it was still around 12.53...I suppose it's dying. I'll get another one and see what happens.

[Kelly E]

You should check in over at kzrider.com
There's some good guys there that know their stuff.

[newday777]

No, it's the one I got for it when I got the bike - it registered 12.53 volts this time after I charged it, but I suppose I should get another one. I was just hoping for enough juice to crank it, or at least trace some problems. Took it back out and it was still around 12.53...I suppose it's dying. I'll get another one and see what happens.

12.53 is fine after charging and waiting an hour for it to settle.
What you also need to do is check the voltage as you and after you try the starter. If it drops below 11 volts and doesn't return to 12.5 then you have a bad cell/internal short in the battery. That is known as a load test.

[Dr. Frankenstein]

I went back out and checked it again as per Newday's instructions, and it DID drop to 11.72. but then went back up to 12.43, - what to make of that I do not know; I'll go check in to KZrider, they keep a light on for me. So I think the battery is good, but why would the bike lights be so dim...?

I checked the ground of the battery, and it's not corroded or loose - I loosened it and re-tightened it too - but I've never had this problem before. The headlight's Hi beam isn't working, but the Lo one is (very dimly), and the turn signals are very dim too -- and No, it won't even Hint at cranking!

I'm thinking "Ground" somewhere - what about you?

[Stev-o]

I'm thinking "Ground" somewhere - what about you?

I'm thinking battery, I always start there with a confirmed good one.  How old is it?
Voltage alone will not confirm a good battery and not sure your load test is giving accurate results. 
Can you "borrow" the battery from your CB? [it may not fit in the battery location but you could just set it close]

[scottly]

If the battery only dropped to 11.72V when the starter button was pressed, I would check both the main ground wire from the battery to the frame, as well as the battery positive connection, which usually goes to the starter solenoid, and then from there to the fuse box for the lights,etc.

[BikerBrains]

So I finally finished up my CB500 Four and am now turning my attention to my '78 Kawasaki KZ650B. I rebuilt this bike - gosh - six, seven years ago after finding her at an estate sale...rode it for a summer or two, and it was awesome, but Time moves ahead and she has sat for a couple years, so it's time ot get her back on the road.

I have a question about the electrical system - I put a fully charged battery in her this afternoon - 12.57 volts - and she should have spun over, but the headlight and turn signals came on really dimly, and the horn was non-existent, but my Question is, where should I start looking for problems first? The rectifier? Fuses? Coil?

I have the same bike. When I had this problem, there was a loose, frayed and exposed wire in the headlight bucket harness that was grounding out. Check all of your wires, the battery and fuses.