Battery good, no engine turnover or headlight power.

Came into possession of an older bike. Does anyone know what is supposed to connect to this 4 prong piece because I feel like it’s missing something but I don’t know what. Bike is a 1977 KZ650(not sure which model). I replaced battery and fuses but only the tail light comes on, and oil light when I turn the key in the ignition. No crank from the starter button or anything.

See:

4 pin connector: What color are the wires? Looks like 3 yellow & a red wire which could be red-green. 3 yellow would be from the stator & red or red-green from the neutral switch, plus you can see that the green wire in the pic goes to the voltage regulator, all of which correspond to the 650-B1 & 650-C1 wiring diagrams. The missing half of the plastic connector would be from the Rectifier.

KZ650.Info >> wiring diagrams
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Rectifier, should be bolted to the underside of the battery tray. Appears to be missing as far as I can see in the photo.

650ed wrote: See:

The pics appear to be of a brand new bike, but I assume that hey are actually your own bike, Ed. Such a fine / clean example of a one owner, all original bike. Compare pics at will.

So I order one for the 650B model and it should solve the next step to getting it to run?

No longer available from kawasaki, you'll need to track one down through ebay. The b model has a different rectifier to others. You need the rectifier with a hole through the middle which is the bolt mount to the battery tray.
Like the one in this link
www.ebay.co.uk/i/273913967603?chn=ps&nor...mEAQYBSABEgK0yvD_BwE

Dont think no rectifier should stop the stater motor turning over or stop the headlight working. Looks like time to check the continuity of all connections and switches.

My thoughts exactly Warren. The ignition should feed B+ to the solenoid coil on one side, and the starter button should ground the other to make the solenoid pull in. It can also be made to crank by jumping across the two large terminals directly. From the pics, your bike looks to have sat in the elements for a few minutes. Perhaps a little like THIS 650. It just needs a little armor all. :S

(BTW. I took this pic. not a pic from the internet )

I guess you haven't seen Will's bike..?

Almost every Kz is wired so the ignition switch supplies 12V+ to the starter button, and the starter button is a momentary 12v+ source for the solenoid's coil which is fed through a black wire. The solenoid's coils is permanently grounded through a red/yellow wire. These are odd choices of wire color and goes against the conventions for Kawasaki wire colors. But that is how many/most Kz's are wired. The OP bike shows a green wire at the solenoid so something's been changed at some point.

Thanks ED, for the reference photos!

As Martin said, the open connector the OP is asking about is from the alternator area, which is comprised of the stator and field coil and neutral switch. It has three yellows coming from the stator. It also has a red wire from the neutral switch. Along side that plug is a single, dark green wire from the field coil, which would have its own connector, but this one has been cut.

The big plug butts up to the metal plate and connects to wiring for the rectifier and neutral light. The neutral light wire is light green with a red stripe. The single, dark green wire goes to the regulator directly. The one on the OP's bike has been cut. Why cut it when it could have been simply pulled off of the regulator connection? The green wire stub on the regulator needs to be re-connected to the green wire from the disconnected wire harness.

The 1977 Kz650 B and C both use the same rectifier. They use the same or similar rectifier as the 74 to 77 Kz400's, so you could use the 400 as a source for used parts if you wanted use factory parts. You could also get a generic 3-phase, 50-amp rectifier and retro-fit it to the bike. They can be had for as little as $5. This is what many people were doing about 10 to 15 years ago.

The 650 and 400 both use the green wire from the regulator to power the field coil. The 650 field coil is grounded to the engine somewhere. The 400 runs a dedicated ground wire (black) for the field coil back up to the main harness, which is an additional wire. (The 400 has two wire harnesses coming from that area, in case you compare harnesses, but it doesn't affect what you need to buy.)

As was mentioned, the disconnected rectifier wiring won't stop the bike from running as long as the battery is good and fully charged.

The 1978 and later Kz650's use a totally different charging system with a single-unit, combination regulator/rectifier.

In taking another look at your pic it looks like the green wire is not cut, but loops around behind the frame and connects to the center terminal on the regulator. Pictures are worth 1000 words as they say, but clear and precise pictures are worth more. It is impossible to see all of the PO's wiring artwork in one pic, although the hawker bunch on the forum see's a lot in your pic.
I was mistaken on the solenoid wiring and the loud one's post is correct. The ignition does feed B+ to the handlebar engine stop switch , then to the momentary starter button, then on to the starter lockout switch (on the clutch lever, not all models), then to the starter solenoid coil which is permanently grounded on the other side of the coil. . Some systems use a green wire for the grounded pole, and black for momentary B+ coil side. The starter solenoid looks to have been replaced at some point (taped connections) . It more than likely had the same problem long before you acquired this gem when the solenoid was originally changed.

This snip from the manual shows the solenoid, the black / yellow ground, and wire from the interlock switch.

loudhvx wrote: .......................The 1977 Kz650 B and C both use the same rectifier. They use the same or similar rectifier as the 74 to 77 Kz400's, so you could use the 400 as a source for used parts if you wanted use factory parts. You could also get a generic 3-phase, 50-amp rectifier and retro-fit it to the bike. They can be had for as little as $5. This is what many people were doing about 10 to 15 years ago.........................

The original rectifier on my 1977 KZ650-C1 failed 7 years ago. I replaced it with one from Oregon Motorcycle Parts, and that one is still working perfectly, so if one is needed that's one place to get a very good replacement for the 1977 KZ650. The part number is R255a-KZ650. It's shown about 1/2 way down in the link below. Ed

oregonmotorcycleparts.com/rectifiers3p.html