TOPIC:

Does anybody know if there's a good plug-n-play replacement for the 4-wire 1976 KZ400-S that doesn't cost 90 to 100 dollars 'Used'?  Z1 Enterprises has one that looks identical for $15, and they say it fits either the 4-wire connector or the six-wire.

Switch - Ignition - KZ650 - KZ750 - KZ900 - KZ1000 - Z1 | Kawasaki and Suzuki Motorcycle Parts | Z1 Enterprises  

 I emailed them to ask about it and the guy said

"Unfortunately, we do not have any KZ400 models listed as compatible with this ignition switch.
So, it would not be "plug and play". 
Thank you for your inquiry,
Sam
Z1 Customer Service Team

Has anybody replaced their ignition switch on a '76 model, and what did/do you use?

I can't advise on another option but I wonder whether that switch on Z1 enterprises is truly incompatible? The Kawasaki part numbers for the ignition switches for the KZ400 S2 and The 77 KZ650 which Z1 shows as a match are different. 27005-089 for the 400 which only turns up expensive ebay options as you've found.

The wiring diagrams for both bikes look very similar (identical?) for the ignition switch despite different part numbers. Both show four wires from ignition switch to a 4 pin connector on the harness. Both have the same connections diagram. Screenshots below.

The only thing I can't find is dimensions for the parts so the switch offered on Z1 may just be too big or small to fit the 400 clock assembly which could be a deal breaker.

KZ400 ignition wiring:
 

KZ650 ignition wiring:
 

KZ400 ignition connections:
 

KZ650 ignition connections:
 

Thanks, those switch diagrams help - so here's the diagram pic:
 

...and here's what the Z1 description says(the red highlights are mine):
"Equivalent to OEM: 27005-086 27005-042 27005-092 - 27019-003 - Replacement Ignition Switch for Kawasaki KZ650B/C/D KZ750B KZ750G Z1 KZ900 KZ1000A-A3/B/C/D 1976 KZ400D3. Fits both 4-pin and 6-pin connector blocks. The 1980 KZ1000 A4 may require some modification as it will not plug directly into the harness. 1979 KZ750-B4: 78 and older used a 4-pin connector- 80 and newer used a 6-pin connector. The 79 had a unique 5-pin configuration. This switch WILL work but may require a little electrical "surgery". REFER to a wiring diagram for assistance."

And here's the Z1 switch:
 

So, yeah, I'm a little confused. It LOOKS like it will work, but the Z1 guy says No; what do you think...? What's the difference between the 4-wire and the 6-wire? What do the extra wires control, and would those be important or otherwise interfere with hooking this one up?  I'm thinking I could just take out the extraneous wires that the 400 doesn't use - if they're not hooked up it shouldn't matter, right?

If I were in your shoes I'd give it a go. Based on the diagrams it might even end up being plug and play but if not I can't imagine the modification to make it work being a big deal.

I think Z1 are in a position where they have to cover themselves because the part numbers don't match so they can't really advise 'give it a shot' even though all the evidence suggests it might be fine.

It reads like the extra wires don't have to plug in to a harness for the whole thing to work and since it connects to a 4 pin 650 the first four pins could be the ones you need to worry about. Sounds like there's no harm having the other two wires not connect since it caters to both 4 pin and 6 pin.

At the end of the day it's your money and you know your own abilities. I'm not a professional but I've repaired wiring on my bikes before so I'd feel comfortable fiddling with the ignition switch wiring for $16 even if I couldn't make it work.

Yeah, I went ahead and ordered one. Strangely enough I already have a 1978 KZ650B in the garage; I compared the switches and figured it will fit. If not, I too can simply 'rewire' it, having some experience with such after having rebuilt the 650 a few years ago, which came to me with a rat's nest of electrical wiring.
Here's a 'Before' and "After' of that bike, btw...
 

After doing some research, I think the 'extra' wiring on the aftermarket switch is for things like 'Park', which I don't use anyway, so it should be fine.
I bought this bike at a garage sale for $200. Somebody had brought the bike in to the repair place/garage for repairs in 1988(!) and never went back for it! 11K on the clock, the tank looked brand new inside, not a speck of rust anywhere; the insides of carbs looked like it had never been run! It's now my daily rider, I love it.  

 

You did a lovely job with the 650! Great find for $200.
Did you clean up the rear shocks yourself or replace? They look fantastic either way but I've always found those such a pain to clean up nicely.
Love that 4 to 2 exhaust as well, looks like it also cleaned up quite nicely!

Thanks, it was a lot of work but I love doing stuff like this. With the shocks (IIRC) I just used a sanding sponge and a Brillo pad to get in between the coils and then washed it up. I was thrilled to find that despite the surface grime this bike was in Really good shape. From what I could find, it looked like somebody had laid it down gently at some time in the past, and then (I guess)  somehow fried the wiring - it was all burned and crispy coming out of the Start button, and I had to take apart the harness to finally track it all down and repair it. It gave me quite the crash course in drop-downs and continuity!   

Just a follow-up, but that ignition switch fits great! It has the proper colors where they should be (white, brown, red and blue), and the two extra are white and green/red, but they are not used. It's going to be a while before I try to crank it over, but the switch had to be replaced since the old one was destroyed. It was a tight fit to get the wires back though the switch holder, but I just took the wires out of the connector, pushed the wires through and reinserted them into the connector. So, Yeah, it fits!

Good news indeed.

Brilliant stuff! Great to know. Glad it worked out so nicely.