Problems; Where to begin '81 KZ750 LTD

Welcome. Pics as you go will help a lot.
Steve

Okay, well in still waiting on my service manual to come in the mail but I've went and taken some pictures. Today I almost got it to start but it let out a loud backfire and shut down... Could that mean the spark plugs or something are hooked up wrong? I made a video, not sure if it'll upload or not but I'll just post all the random pictures I took and maybe a problem will stick out to one of you guys. If not, I'll just wait on the service manual and trace one thing at a time. Thanks guys.

I included a video of me demonstrating how it tries to start in the off position, but does nothing (lights come on) when I turn the key on and try to start it. I flipped the key from off to on real fast while holding down the start button, which casued a backfire, so I stopped doing that.

I also included a picture of my spark plugs and wires, in case someone can tell if they're hooked up wrong or right, I tried to lay the wires so they were easily traceable in the picture.

You don't have a battery in it yet? Pic 4 looks like the stop lamp failure relay connector. I'd get rid of the quick splice connectors and go from there.
Steve

No disrespect intended but from the looks of the photos you got yourself a long neglected vehicle on your hands.

Different people have different approaches to getting a vehicle like that back on the road but at minimum I'd do the following before even attempting to start the bike:

- Remove the carbs and tear them down (ungang them). Soak all the bodies and loose parts in carb dip, then reassemble with fresh O-rings everywhere.

- Pull valve cover and check/adjust the valves as required and install new gasket.

- Replace air cleaner and replace any carb/airbox boots that are not soft and pliable.

- Dump out any old gasoline in the tank and flush/clean. If there is any rust then clean it out. Lastly verify the petcock is working properly and not leaking, both internally and externally.

Not sure what to even say about the electrical system. It looks like a rats nest. At minimum I'd check for voltage loss between the coils and battery and check for strong spark on each plug before attempting to start the bike. Needless to say all the various electrical connectors need to be taken apart and physically cleaned. This in itself is no trivial matter. One thing at a time though...

Good luck

Right side coil --- 1-4 spark plug wires --- red & black igniter wires.
Left side coil --- 2-3 spark plug wires --- red & green igniter wires.

Image 2. probably the red power wire from the voltage regulator & is bullet connected to a red/white wire that goes to the starter solenoid pos (+). you'll have to trace the wires to verify.

Image 3. yellow/black is typically a ground wire, but I can't tell where it terminates.
Maybe the ring connector should be connected at the battery neg (-). ???

Image 4. could be for the low fuel switch from the fuel tank.

Image 5. The big connector is probably the ignition switch. the green should mate with green --- maybe the tachometer. There should be a blue/white accessory terminal (typically unused) & a black/yellow accessory ground terminal (also typically unused). Plus other stuff you'll have to figure out. speedo & pilot box lights. handlebar control switches. clutch switch. brake light switch.

Image 6. The red connector may be something to do with the turn signal canceling unit or the reserve light device. ???

Image 7. shows the accessory fuse box w the black/white accessory terminal.
There's also a blue/white accessory lead that terminates at the headlight bucket.

Thanks for taking a look for me guys. I do have a battery, I just had it out when I took the picture. This is how I acquired the bike, so no disrespect taken, I am aware of the ugliness of it lol. I am getting the feeling that I have no business messing with this, I'm no mechanic. Hopefully I can get my money back out of it at least ($400). I'll save up and buy something that already runs and avoid the headache and feelings of defeat. Thanks again everybody.

Pics of the whole bike? might be worth saving.
Steve

+1 on all the things that Nessism suggested.

For me the gas tank comes off and is checked.
Carbs off and cleaned
Hand wash the bike with some wet rags, I don't like to get bikes too wet when I am first starting to work on them.
Then I get some good lighting going with some good pliers. The air compressor is handy along with dialectic grease for all the connections. With the age of these bikes and different lengths of weather/sun damage, you really have to look close at the wires. Some wires might be cracked or broken. Just have a open mine to the fact that you might have to replace some of the connectors or even add good wire in places that old wires are.

From your starting situation above, you might even want to remove the ignition switch, open it up and clean out the contacts. There are many "how to vids" if you look for them.

Just stick with the trouble shooting and stay positive with little things that start to work out. Starting from a known "Good" with the electrical system is also a good practice. Either from the battery side through the circuit or from the ground side. Once you get the wiring diagram you will have to look it over real well and get used to the color codes of the wires.

No eBay APP ID and/or Cert ID defined in Kunena configurationOkay guys, I think I have a solution for my non mechanically inclined self... A whole new wiring harness. Is this a possible solution or am I wasting my time and money?

Not for that kind of money. I would repair what I already have using the wiring diagram in the manual.

If you can afford it and it is correct for your bike, it might be a good move. I'd rather see pics of the plugs and other things first. Maybe a wide angle shot of the wiring stem to stern with close ups on trouble areas. Carb bowls, mounts, points/pick ups, etc. A valve adjustment as well.
Steve

I agree with Swest, better pictures and a little time with a diagram might be all you need.



This above picture, is for the fuel light indicator on the tank.



This one looks to be the starter solenoid ground...maybe

Your spark plug wires are definitely not stock, a picture of the coils and plugs could help us to help you.