1979 CB 750K - Are there supposed to be loose wires in the headlight assembly?

[cbwithagb]

Hey everyone,

New member, first time post! I searched through previous posts here but couldn't find a similar problem to the one I'm facing. I think it might be really obvious but I'm still very much new to motorcycle repair so sometimes I don't notice a lot of things.

I picked up a real dinosaur 1979 CB750. It was stored for a heckin' long time. The previous owner must have prepped it for long term storage. There was no brake fluid, oil, or gas in it. So I'm assuming that all the wiring is intact.

However, once I put a battery in, only the brake light comes on and stays on. The headlight only comes on if I push the key all the way to the right, or if it is between the on and ignition slot. Sometimes it stays on in the ignition slot.

Earlier, the indicators were working briefly (but they weren't blinking). There was also a brief flash of the "oil" light came on, too. But that was for a split second.

I figured I should change the fuses, so I did, but that didn't fix anything, and now the indicators don't work but the brake light still goes on and stays on.

So, I opened up the headlight assembly to have a look. I found three loose wires. A green one, a brown one and a black one. (They aren't loose, they have that plastic tubing around them.) I looked at the wiring diagram (picture attached) and these wires just end. Is that supposed to be the case? I traced the green wire and that seems to be ground.

If anyone has any suggestions on how I can fix this, I'd be really grateful! All I want to do is get this baby running before my holiday ends in two weeks. If I can't, I might just have to sell it for parts ):

[TOOLS1]

Those wires are supposed to be like that in the headlight. The green wires are grounds, and the black wires are switched hot. It sounds like you have some dirty/loose connections, and a bad ignition switch. Start with taking every connection apart (even your battery cables, and handlebar controls) clean them (I use a dremel with a wire wheel) and put them back together with some dielectric grease on them. As for the ignition switch, it is actually a cheap little plastic part the is mounted to the bottom of the key cylinder, and is very easy to replace.
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[cbwithagb]

Thanks for your reply. Electric stuff is my least favorite thing to do, but now I have to!

I'm going to start by assuming nothing. Will get a multimeter today and check the voltage of the battery first. Will continue to use the multimeter to check that connections are good after cleaning them, too.

This is my first time doing anything like this, I hope Honda's are as simple as they say ;)

[cbwithagb]

Is this the replacement part on the ignition?

http://www.ebay.com/itm/Emgo-Honda-Ignition-Switch-Repair-Kit-CB650-CB750-CB900-CBX-40-15800-/172611938472?hash=item28307928a8

[TOOLS1]

Yes, that is the ignition switch.
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[cbwithagb]

[cbwithagb]

So, while cleaning connections I came across this wonderful mess. It looks like the tape has melted around it and onto it. It was bolted at the top but open at the bottom.

What part is this? It's behind the battery compartment in front of the rear wheel. What the heck happened here? Fire? How do I fix this?

[cbwithagb]

So, after looking around at various parts, it turns out that that is the CDI box.

Does the CDI come in two parts?
On ebay, some people are selling the spark unit, some people are selling the ECU. I thought an ECU and CDI were different things?

Anyway, it turns out that a complete unit is like $100. Any chance of being able to build one? Bite the bullet and buy it? Alternative models that I can also search for? Scrap the bike yet? :P

[TOOLS1]

They are most commonly referred to as "spark units" and they do melt. I would try to find some used ones on e-bay. Several models used them, so they should be easy to find.
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[cbwithagb]

Yeah, I ordered one on ebay that's been tested and is good. Not the cheapest part but what can you do? When it arrives I'll post back here with an upate.

[cbwithagb]

Alright, here is the general update:

Battery is charged at 12.8v, the controls light now up and the indicators just stay on.
The ignition is sticking and has to be jiggled and held in place to get the electronics lighting up.
New CDI is in, hasn't made a difference.
When I hit the start button, the battery just clicks.

I think the problem is with the starter motors?

It feels like the bike is fighting me at every turn. I spilled some gas when putting it in the tank and it took some paint off.

Sigh...I just wanted to be doing carburetor maintenance. Now I'm struggling with electronics. Not enjoying this restoration!

[cbwithagb]

I think it might be the battery. It's at 12.4v now, and when I try turn it over the voltage drops to about 7.

[TOOLS1]

It might be the battery. Have you tried jumping across the solenoid?
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[cbwithagb]

Apparently if the voltage doesn't hold above 10v for 30 seconds, it doesn't have enough power to turn the motor. The voltage on this batt just steady declines when trying to turn over.

I bought a cheap battery from Napa. Gonna take it to them tomorrow and see what the deal is. If they say it's OK, then I'll look up on how to do that jump across the solenoid.

[TOOLS1]

Just take something metal, like a screwdriver, and touch both of the big wires (battery cables) connected to the solenoid. This will make a solid connection between the battery and starter.
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[cbwithagb]

I got a new battery earlier today, charged it up to 100% and the same problem continues.

I can definitely hear the solenoid's one click. I don't think that's the problem.

Tomorrow I'm going to remove and check the starter motor. In the service manual for the CB750K it doesn't mention removing the carburetors to get to the starter motor? What do you reckon?

Also, when the lights are on the turn signals don't blink. They just stay on. Could that possibly be related to this problem?

Sure wish this bike had a kickstart!

Something that I noticed is that under the gas tank there are two oval metal containers that look like starter motors, but I can't find anything in the service manual about what those are. Any ideas?

[TOOLS1]

Just because the solenoid is clicking does not mean it is working. You can test the starter by jumping across the solenoid. It is a lot easier then removing the starter. I do believe that the carbs need to come off to give room for the starter to come out. On the turn signals, you must have the headlight cross wired into the turn signals. Probably through the indicator light. I cannot imagine what looks like starter motors under the tank Unless you are referring to the ignition coils.
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[cbwithagb]

Yeah I jumped across the solenoid, and still nothing.

Took a long time to pull the carbs, they were really jammed in there, but they're looking quite clean.

Got the starter motor out and tested it with the battery. It sparks but doesn't jump. Reckon that's the problem after all!

So, a rebuild is quite complicated. I found a working CB550/650 starter motor for $30 on craigslist. It looks the same as the one I have. Will it work in a 750?  

[TOOLS1]

Here is a list of the ones that cross over to your bike.
http://www.partzilla.com/parts/detail/honda/HP-31200-438-505.html
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[cbwithagb]

Sweet thanks!

I took apart the starter motor this evening and there was some rust on it. Cleaned it up and put it back together but still no dice. Ordering a new part now.

Oh the joys of old bikes. This one doesn't want to wake up!