TOPIC:

Buddy of mine has a 1978 KZ650 with some strange electrical issues. The starter is always hot even with ignition and kill switch off. But even though the starter will engage at anytime it wont start unless you....

Hit starter button and then while cranking turn the key on! If you turn the key on and then hit the starter button it will crank but never fire. (clutch switch is bypassed)

Today we set out to figure why the starter button is always hot and found some wiring is wrong by the schematic we have.

The red/yellow wire off the starter relay was tied to a hot wire straight off the battery and then tied into the red/white wire that runs from the rectifier to the 20A fuse.

The schematic we have shows that the red/yellow wire from the starter relay goes to the black/yellow wire. The black/yellow wire is the main ground for everything correct?

So we went about changing these wires to be how the schematic shows. Then the starter, kill switch and ignition switch all worked like normal. Problem solved we figured. Well, after a few mile test ride the bike died, completely dead battery. After jumping the bike we checked and have no charging at the battery. We put the wiring back how it was and now its charging. ???? I'm kinda stumped here, anyone have any idea what could be going on?

It looks to me like the red/yellow wire off the starter relay should go to ground thru the yellow/black wire. But if I do that then I get zero charging with the bike running even though then the ignition switch works like it should.

Any ideas on what to check next?

It sounds like someone in the past did some - lets call it - creative wiring. The 78 650's came stock with a single phase permanent magnet charging system that had a combo regulator/rectifier unit.

There should be 2 yellow wires coming from the alternator to the combo unit and a black/yellow ground from the combo and a red/white which feeds the battery.

When you hook the red/white from the starter relay to the black/yellow ground, what are you doing with the red/white that it use to connect to? You many need to plug it into the red/white from the combo unit as it needs to feed the + post on the battery.

The red/yellow off the starter relay does connect to the black/yellow wire grounding circuit.
Being red/yellow, I would have thought it would be a positive 12 volt power supply, like all other red/yellow wires (well most it seems).
Someone else mentioned just the other day that this red/yellow wire off the starter relay hooked up to ground.
I looked in a manual and it comfirms this.
There is a red wire attached to the starter solenoid, to one of the large connections, that is a power feed (12 volts) and in circuit with the red/white that comes off the voltage regulator.

Check that the voltage regulator is working properly, and wired correctly, as per the manual.

First - Just in case....make sure the engine is truly a 1978 model. There were several different charging systems on KZ650s depending on the year. Here's where you can check the engine serial # against the model years:
models.kz650.info/index.htm

Once you are positive about the model year of the engine; here are wiring schematics that may help:
diagrams.kz650.info/wiring/WiringDiagrams.htm

The wiring you changed to would be correct for not sure with present how this would work the way they had it.... 12Vdc on both ends of control coil. May explain why hot all the time though...

Here's the skinny....

As can be easily reviewed in this KZ650 3 phase dynamo image. (yours may be 2 phase) but truly doesn't matter for what you're T-shooting for.

Starter Control relay:
* Starter button passes battery Vdc (+12Vdc) to starter relay.
* Starter relay coil other side is grounded.
* Through starter button press, coil plunger is energized and pulls down to pass 12Vdc from battery to starter motor.

Pretty simple when you think about it...

Easy test, wire as bellow should work fine.
NOTE: Insure your engine/frame is ideally grounded (no rust/oxidation/paint etc... on terminal connection)

NOTE 2: Insure Black/yellow conductor from your regulator is at battery ground potential!

Here is a photo to show what we are working with. This is after we undid everything and put new connectors on. When we undid everything stuff was just twisted together and taped.

From the top down in the photo....

red/white wire off the relay is tied in with the positive straight off the battery

red/yellow off relay

red wire with blue female bullet connector (just to the left of red/yellow wire) ties into the red/white wire which you also can see at the bottom of the photo attached to the red wire from the rectifier

black wire with blue female bullet connector (lower left in photo) ties into the black/yellow wire which can also be seen coming out of the plastic connector from the rectifier. We had to add this wire. If wiring had been original I would have questioned why we had to add a wire, but since all this was such a mess it didnt surprise me that we had to add a wire. We added this wire to tie into the red/yellow wire off the relay.

Could there be something wrong with the starter relay causing it to feed voltage to ground thru the red/yellow wire? Because when I connect the red/yellow wire off the relay to ground thru the black/yellow wire it does not charge while running.

Maybe this is why someone tied the red/yellow in with the hot wires? But then making the red/yellow wire hot on the starter relay causes the starter to be hot always?

How can I check the starter relay?

One thing that confuses me a bit is that you have a green wire coming off your regctifier/regulator - that would suggest either an aftermarket item or a Honda unit.

The stock 650 1-phase rec/reg should have 5 wires: two yellow (stator), red or red/white (output to battery +),
black (ground/frame) and brown (voltage sense wire that should connect to a switched 12V source to sense
system voltage).

Some rec/regs haven't got the sense wire and sense system voltage internally in which case there's no brown wire.

It's a bit hard to tell from your pic if your rec/reg has 4 or 5 wires (looks like 4?), but if you have an aftermarket unit and the yellows, red and black are there, it would seem likely that the green wire is the sense wire.

However, if it's a Honda unit be aware that Honda uses green for ground - from your pic it seems that the green wire connects to a black/yellow (ground) which would be correct for a Honda unit.

Does your rec/reg have any markings/numbers that could help identify it?

I have a B2 that, according to the frame number, is made mid-run of the B2 series. It still have the old 3-phase charging system and wiring harness. Well, had until I transferred it to my B1 that, to make things confusing, run a F1 engine.

Not to start an argument here but the 78 models with the single phase systems came stock with a 4 wire reg/rect combo unit. (2 yellow, one red/white and one black/yellow) So I agree from the pic posted it is not one of the stock units on the bike.

I would be making sure the red lead from from combo unit connects to the battery. Trace the red/white lead you have plugged the red lead into and have indicated leads to the fuse as it should also connect to the battery + side. If it does not then you need to make it do so.

I stand corrected, Bruce. The 78 models (B2, C2 and D1) do indeed have a 4 wire rec/reg, the rest of the single phase systems (from the 79 models up to they switch to 3 phase) have a 5 wire.

The rectifier is a new unit from Z1E, box said Ricky Motorsports on it. It has 4 wires, 2 yellow (stator), green (ground), red (power). The red wire does for sure go back to the battery thru the red/white wire.

We messed with it again today after charging the battery overnight on 2 amps. I borrowed a good digital multimeter from a neighbor today to recheck everything.

It is infact charging with everything hooked up correctly. (red/yellow starter relay wire to black/yellow ground wire instead of red/yellow relay to the hot red wire) But the charge voltage is WAY too low.

We are getting 12.02 at battery with engine off, 11.45 at idle and 12.04 at 2500rpm. He reved it up all the way to 5000 and still showed only 12.80

We checked the two yellow wires off the stator and are getting 70 volts AC @ 5000rpm on each wire.

Is there an easy way to check the rectifier? We went thru the Fault Finding Guide on Electrosport found here...

www.electrosport.com/technical-resources.../fault-finding-guide

...and made it thru sections A and B and got to section C where the DIODE-TEST stuff starts. I had no idea how to set the meter for DIODE-TEST, but everything up to that point passed the test.

I'm kinda thinking its the rectifier, just because its new doesnt mean its good. I'm also a little suspicious of the battery, shouldnt it be showing more like 12.75 volts after charging all night? It was showing 12.02 volts.