TOPIC:

1976 Kz 900. Tested all three yellow wires at the "patch panel" socket and getting 11.6v-11.8v at idle, 33v-35v at 2,500rpm and 46v-48v at 3,500rpm. assume stator is good.

But, at 2,000rpm, reading across the battery terminals is 11.8v and reving makes absolutely no difference.

Bike is running very well but obviously having to start using kick start.

Guidence on how I test the various other pieces of the equation needed please. Thanks.

BH

Hi,
I came across a very helpful document for troubleshooting the charging system on most motorcycles.
Here is the link
www.electrosport.com/electrosport_fault_finding.html

At the bottom of the page is a link to download the flowchart in PDF format. You can follow step by step to diagnose your problem. Hope this helps.

Al

Barney... making an assumption that you have the stocker KZ900 electrics... Your regulator is bad. The stator tests seem to look OK but your battery voltages are not. The only thing that can cause this is the regulator which is located under the battery box and uses the green plug in to your junction panel. While you can test the regulator (do you have a manual?), the thing I would do is FIRST check your wiring. There is a brown wire and ground on the regulator. I can't recall if these flow through the green plug or there is a separate wire outside the plug. The plugs make things handy but make things harder to troubleshoot. Anyway, the brown wire feeds voltage back to the regulator. This is a feedback loop where this voltage level on the brown wire is what allows the regulator to make a decision on what voltage level to put out... bad connection on the brown and the regulator will act like it is broke. Trace the brown connection; it is just a switched 12VDC wire. The brown circuit also powers your horn and the emergency flasher circuit. Check the ground wire. I think it connects to a ground wire coming off the solenoid. Make sure this connection is clean and tight.

The three yellow wires actually split after the blue connector and go to both the regulator and the rectifier bridge located behind the solenoid. They come together via a white wire (it might be white with a red stripe... can't recall). This white wire goes to a double connector and a white wire goes to the POS terminal of the battery via the solenoid lug where it connects and hooks with the main battery cable and the other leg goes to the main fuse. Look at these connections, especially the connection to the solenoid lug... make sure wire ends/connector is clean and tight.

If the connections are good, look for a new regulator and just plug it in and give it a shot or buy a new regulator/rectifier from z1enterprises.com - they sell Rick's brand and these are good components. This will require some minor rewiring but probably something you can do pretty easily.

Why is his rectifier out of the question? A broken rectifier could cause the same problem.

If the regulator is good, but the brown wire becomes disconnected, you will have too much voltage, not too low.

Have you checked the stator wires for continuity to ground (while disconnected from the reg. and rec)?

After checking wiring, and charging the battery for a couple hours, the next step would be to let it idle and disconnect the regulator. If the regulator was bad, and pulling down the voltage, it should go up whendisconnected. Be careful to monitor the battery voltage the entire time. The meter should be connected permanently or with very secure alligator clips. You'll have your hands full with other things. If the voltage goes above 14v turn the bike off immediately, and the problem is a bad regulator. If the battery voltage does not go up, rev it a little and see if the voltage ever goes up. If it ever reaches 14, then the regulator was bad.

If the voltage never goes up, then do the same checks but check the voltage at the output of the rectifier, using the rectifier's output for the red meter lead, and the rectifier's ground wire for the black meter lead. If the voltage is good at the rectifier output, then it is a wiring problem.

If the voltage never goes up past 13 or so, then it is most likely the rectifier.

If you want, you can load test the stator. Disconnect the stator from the rest of the bike, then make little jumpers to connect one pair of yellow wires at a time to a spare 55w car headlight (or spare motorcycle headlight). Now connect the meter to the headlight as well. Put it on AC-voltage and let it idle. Revving the bike should easily get it over 13v AC. BUT BE VERY CAREFUL. IT IS VERY EASY TO OVER-REV THE BIKE AND BLOW THE BULB. Make sure it is not a bulb you care about. Do the same thing using different pairs of yellow wires to verify any two yellow wires give good voltage.

This is all excellent information and looks fairly straight forward to follow. Thank y'all (Tn term).

What I would say is that I have, over the past year, changed out both the rec & reg. I actually removed the whole patch panel/rec, soldered and shrinkwrapped all the joints in the mess of wires behind the pach panel. i also did the same with all other rec & bullet conectors going elsewhere from the rec.

The ONLY wire I am not 100% on is the brown wire mentioned by WG. I feel this may well be my problem.

I had seen noted elsewherere on the site by WG that I could pick up a new switched 12v+ from the lead going to the rear light. This I will do.

I'm assuming that i can tell if the existing brown wire in the patch panel socket is good by starting the bike, disconnecting the reg' plug from the patch panel then inserting the red lead from the meter on the brown wire hole and the black meter wire to ground. Should read 12v. Yes?

Thank you.

That is a good question... think about it a second. If the brown is switched VDC, it should be the same as the battery voltage at most any point because battery is getting the hot feed from the reg and rec. If you unplug the green, that disconnects the reg from the rec so you would just get whatever the battery is putting out without being in a charging state... I guess 12VDC would be about right. I doubt it could go much higher if my thinking is correct. I don't think this will test much except that there is continuity through the brown circuit to get you the voltage, if that is what you are looking for.

Barney... btw: when I was a kiddo in TN, I am thinking we said YOU-UNS and not ya'll... Course this was in the hills and such.

WG, You would be correct, YOU'uns is actually the gramatically correct term BUT is usually only heard in the far eastern end of the great state of Tn.

Correct usage might be "I'm fixin' ready to beat You'uns round the ear'ols".

BH

The only way the brown wire, alone, could cause your symptom (voltage too low) is if it had 15v or higher on it. You can't get that if the battery only has 12v on it. If the voltage on the brown wire is too low, the regulator thinks the battery voltage is too low so it gives more power to the battery.

That's why the symptom for a bad brown wire is that the battery voltage gets too high.

There has to be a different problem involved besides just the brown wire, on your bike.

Ok, here's what i know so far....

Leaving the brown plug plugged into it's socket on the patch panel, I "back probed" it (doesn't sound good does it).. At 1,200rpm the brown wire is giving me 10.52v, at 3,000rpm it's showing 10.70v, rising slowly over a minute or so to approx 11.10.

At the same 1,200 rpm across the battery terminals, I'm getting 11.72, about 11.90v at 3,000rpm, rising again, slowly over a minute or so to 12.07.

What do we now know?

The brown wire is just tracking your battery voltage. It is lower than battery voltage because you apparently have a bad connection along the battery-to-brown-wire path.

The voltage is very low and you need to charge the battery before it's damaged.

Outside Sweetwater yoo-uns was the only way to talk. Ya'll is more Texan. Anyway, BREAK DOWN AND BUY A NEW COMBO REG/REC; clean up your wiring and use some new connections... heck, if you want to do it right, put a new fuse box with modern fuses at the same time. I suspect the regulator as the regulator is out of the airflow and is what goes bad most of the time... just experience. Could be the rectifier bridge but they seldom have issues. I think they can be tested per a manual...