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I just bought my first project bike, a 1980 Honda CB750K, and I'm going in sort of blind. I have some mechanical small engine background but am looking for some help here.

Went to attach the starter solenoid and plugged it in. The bike was missing any other wires or cables for the solenoid. I found another positive cable in the extra parts given to me and attached it to the solenoid.

I then found what appeared to be the connection to the starter motor, and attached that. I then put in a brand new battery and attached the connection from the starter solenoid to the positive terminal. I then grabbed the ground and attached to the negative terminal. All seemed pretty straight forward.

I then put in the key, turned to on, and pressed the start button. Nothing. Not even a sound. I checked the ignition fuses and they appeared to be good.

Any suggestions? Im not sure if the starter motor is bad, if there are additional fuses to check, or where to begin. I'm now wondering what to check next, as far as electrical goes. Thank you!
 

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I then found what appeared to be the connection to the starter motor, and attached that. I then put in a brand new battery and attached the connection from the starter solenoid to the positive terminal. I then grabbed the ground and attached to the negative terminal. All seemed pretty straight forward.
If the only wire you attached to the battery's positive terminal is the heavy wire going to the solenoid, that won't work. The rest of the bike's systems also need power from the battery, i.e. the battery supplies power through the starter pushbutton switch to activate the solenoid.

I don't have firsthand knowledge of the CB750K, but I did have a CB900C, and on that bike (and the other bikes I've owned) there were a couple of wires attached to the battery positive.
 

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If the only wire you attached to the battery's positive terminal is the heavy wire going to the solenoid, that won't work. The rest of the bike's systems also need power from the battery, i.e. the battery supplies power through the starter pushbutton switch to activate the solenoid.

I don't have firsthand knowledge of the CB750K, but I did have a CB900C, and on that bike (and the other bikes I've owned) there were a couple of wires attached to the battery positive.
Aside from the 4 wires that plug into the solenoid, I didnt see any other wires, especially not with ends that go on a terminal. This was what made me curious about missing wiring in the first place.
 

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You need to search for a wiring diagram for that model/year bike before you go any further. You could easily fry something by putting wires in willy nilly.
 

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Went to attach the starter solenoid and plugged it in. The bike was missing any other wires or cables for the solenoid. I found another positive cable in the extra parts given to me and attached it to the solenoid.

I then found what appeared to be the connection to the starter motor, and attached that. I then put in a brand new battery and attached the connection from the starter solenoid to the positive terminal. I then grabbed the ground and attached to the negative terminal. All seemed pretty straight forward. ???????
 

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You should see if you can find a factory manual with a wiring diagram. If it is anything like my old Suzuki the starter motor probably gets it's ground from the motor where it is bolted to the bike. If it has a an older type of starter solenoid like on a riding mower it has two heavy terminals, one positive in and one positive out to the starter motor brushes. There will be a smaller wire from the starter button to the solenoid coil to lift the main contact to connect the two heavy positive terminals. The ground for the other side of the solenoid coil may be be the plate it is bolted to. On my bike, that plate is isolated with rubber gromets to damp vibrations for the electrical components attached to it and has a separate ground to that plate. If that ground is missing the solenoid will not work. If the main ground from the battery to the frame or motor is coroded the starter will not work because it will be missing it's ground. Those heavy stranded cables are famous for hiding corosion at the terminals and may need replacing. I would check both positive and negative cables to the battery first because everything depends on them being good, the starter solenoid next and the starter motor brushes last because you will have to remove it and take it apart to do that. If that doesn't fix it you need to check the starter button itself and it's wiring. Think about finding a parts bike just like it if it is cheap enough so you have a possible ready source of parts. Babbits online Honda has good diagrams and many parts that you might need. Good luck!
 

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If your bike is wired anything like the schematic you will find here: CB750K then it is pretty simple.

An inexpensive voltmeter is a very good investment. An ohmmeter is also a handy thing to have. Not exactly a precision tool, but for $6.50, well worth the expense for somebody in your position: 7 Function Digital Multimeter

Some basic understanding of electric circuits is important. If you read and understand this article, you should know enough to fix your bike: Electrical Circuit Basics | 12 Volt Planet

Later, you might want to read up on capacitance, inductance and how power is generated via electromagnetic flux. I'd recommend this book to any mechanic who worked regularly on motorcycles and felt they would benefit from more knowledge on electrical systems: Motorcycle Electrical Manual by A. Tranter; Tony Tranter 9781859604717 | eBay

I'd probably proceed as follows:
Check the new battery voltage. Check it's state of charge by hooking it up to a decent load like a headlight and verifying that voltage doesn't sag too much. I'd be using jumper wires for this test.
I'd bypass the solenoid and use jumper cables to verify the starter motor.
I'd disconnect the starter motor and verify that the solenoid closes when triggered.
I'd verify that the ignition switch contacts closing is delivering power to the system.
I'd verify that the starting switch contacts are closing. I'd verify the starting switch ground.
I'd verify the wiring interconnecting these various points.

I'd bet that the problem is with the starting switch ground, or the starting switch contacts, or the ignition switch, or connectors somewhere in the wiring.

Good Luck!
 

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Not exactly a precision tool, but for $6.50, well worth the expense for somebody in your position: 7 Function Digital Multimeter
I've had one like that only yellow for years. Gets the job done. I only recently got a Fluke because we needed something the cheap thing couldn't do while we were working on our solar panels.
 

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I've had one like that only yellow for years. Gets the job done. I only recently got a Fluke because we needed something the cheap thing couldn't do while we were working on our solar panels.

When HF had those on sale for 3-4 dollars I picked up a handful. Had one on the boat, one in the tool box in the truck, one in my little car and one in the house. I also have a fluke for serious stuff. My neighbor turned me on to this tool and I had to have one Power Prove It is magic working on 12 volts.
 

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I just bought my first project bike, a 1980 Honda CB750K, and I'm going in sort of blind. I have some mechanical small engine background but am looking for some help here.

Went to attach the starter solenoid and plugged it in. The bike was missing any other wires or cables for the solenoid. I found another positive cable in the extra parts given to me and attached it to the solenoid.

I then found what appeared to be the connection to the starter motor, and attached that. I then put in a brand new battery and attached the connection from the starter solenoid to the positive terminal. I then grabbed the ground and attached to the negative terminal. All seemed pretty straight forward.

I then put in the key, turned to on, and pressed the start button. Nothing. Not even a sound. I checked the ignition fuses and they appeared to be good.

Any suggestions? Im not sure if the starter motor is bad, if there are additional fuses to check, or where to begin. I'm now wondering what to check next, as far as electrical goes. Thank you!
If you have checked continuity of Stator and coil and they are good, check your ignition key switch- sometimes they twist out of scink. This throws electricity in all kinds of odd directions. Very frustrating.
 
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