77 KZ650 Weak Charging

I finally got my 1977 KZ650B1 wired up and running. It's a super basic system: ignition/kill switch, 3pos headlight switch, horn button, LED tail light, electric tach, kick start only, Dyna S ignition & 3ohm coils. Everything is new, including a combo reg/rec from Z1E and a fresh battery showing 12.86V.

As soon as I turn the ignition switch to the on position (tach, tail light and coils), it drawing 8amps and battery voltage drops to 12.2V.
When running and warmed up, it stabilizes around 12.4V and charging doesn't vary between idle and 5k rpm. I've read the '77 3-phase system draws a lot of juice with the ignition on but should be hitting 14.5V no problem when running.

I've gone through the '77 Service Manual charging system diagnostics and the Electrosport Fault Finding Diagram. RR passed the diode tests, continuity across all connections checked, and zapped myself with 70VAC across the legs leaving the stator. If I remove the brown wire to the RR, voltage drops to 11.8V and will come back up to 12.4V when I plug it back in... so it appears to be trying to charge.

Going crazy trying to figure this out - this is why I stick to mechanical problems. Any ideas are welcome!

Battery may have a bad cell.
Steve

Steve- I thought it may be a bad battery too so I swapped out my Shorai lithium with a lead-acid fresh from the dealership.

Same results with both. So either I'm very unlucky at buying batteries, or there is something else amiss.

Confirm your battery negative main wire and negative main wiring connector is connect to the engine housing and bike Frame
at a bare metal common point. A fresh powder coated frame will insulate or disturb the current flow in a electric wiring system.

Does your bike have a conventional 3 phase AC charging system or a field coil system? If the former it sounds like the R/R is hooked up wrong.

And BTW, a no load AC test on the stator is no guarantee that the generator will make enough power to hit 14.5 vdc at the battery. You should be doing better than you are though.

Scirocco - Interesting point. I only have the ground going to a bolt on the engine case and figured the motor mounts would tie into the frame. But everything other than the threads would be contacting powder. I'll play around with this.

Nessism - It's the oddball system on the '77 with the 3 screws on the side cover and stationary field coil. R/R is wired up: Red to positive post, black to negative post, green to stator, 3 white to stator, brown to key-on power (tapped from tail light). Please let me know if I'm backwards here.

Could be an open circuit on one of the stator phases. I've had this happen.

It appears you have an aftermarket regulator/rectifier. Were you able to perform the max-field test? That is when you route full battery power to the field coil while the motor is running. While doing the test, you should note the voltage on the field coil at the green wire. It should be the same as the battery since you are connecting the brown wire to the green wire. Likewise, you will also need to find what the negative side of the filed coil measures. That should be connected to ground so it should be at 0 volts. If not, then the field coil may have lost its ground or has a bad ground. This will reduce the potential output of the alternator.

You are using a Dyna S which is using more than double the current of the stock points. This leads to heating of the main fuse and voltage drops along the path feeding power to the field coil. This will cause the output of the alternator to drop when the regulator is asking for maximum power output.

This is one reason why a better regulator/rectifier design uses an auxiliary output on the rectifier dedicated only to powering the field coil. This also eliminates the massive current draw of the filed coil when the motor is not running. I have a design showing this option. It is the three extra diodes feeding the regulator.
s3.amazonaws.com/gpzweb/RegRec/GPZvRegExciteField.html

There are other possibilities too, like stator condition, as was mentioned.

GrantKZ650 wrote: Steve- I thought it may be a bad battery too so I swapped out my Shorai lithium with a lead-acid fresh from the dealership.

I'm with you on the electrical problems and will need all the help I can get on here if I start having problems....... hoping you find it so you go back to that lithium battery..... something that's been on my Christmas list for a while now.

GrantKZ650 wrote: .................... It's the oddball system on the '77 with the 3 screws on the side cover and stationary field coil. ..............

Actually, that "oddball system" works extremely well as long as it isn't modified with mismatched components. Mine has worked fine for the past 42 years (61K+ miles) other than needing the rectifier replaced after about 52k miles. Troubleshooting that problem was simple since the Kawasaki Service Manual gives easy to follow instructions.

I believe most charging system problems arise when folks install ignition systems, coils, combo regulator/rectifiers, etc. that do not comply with the stock specs. At that point troubleshooting problems becomes a crapshoot since the mix of standard and non-standard systems may not play well together. Ed