79 Honda CB 750f fuse popping

[dietCB750SS]

I have a 1979 CB 750F that has been giving me some trouble. Whenever I plug the harness into the starter solenoid, (the thing that has the 30 fuse in it by the battery,I think that is the solenoid?) the fuse on the solenoid pops. If I unplug the red plug on the wiring harness that goes to this thing that is pictured everything will come on (with no key in the ignition) and the bike will not start. I replaced the harness with a used one from ebay and got the exact same results. I am told, by a family friend, that a Dyna ignition will solve all of my problems, but I am hoping to spend less than 3-400 dollars.

(What is this thing?)

Any ideas would be greatly appreciated.
Thank you,
Jerry

[TOOLS1]

Those are you pickups/triggers for the electronic ignition. I have not heard of them shorting like that, so I would bet that there is a short somewhere in that circuit that you just need to track down.
TOOLS

[dietCB750SS]

Would the rectifier be on that circuit? I think I read on another forum that a bad rectifier can cause the fuse to pop like this

Thank you for the insight Tools1

[TOOLS1]

I doubt it would be in that circuit, but am not really familiar with the DOHC wiring. You can download the factory service manual from the manuals thread at the top of the home page here, and it has wiring diagrams. That would show what is on that circuit.
TOOLS

[dietCB750SS]

I think I want to try replacing the ignition switch and go from there. But I do not see how to remove it. I have removed the wire connection from it, but I do not see where to go from there.
How do I remove the switch?

Nevermind, I got it off, ordered a new one, I will try replacing it next week

[dietCB750SS]

I have narrowed it down to a bad ignition oil or the spark advancer. I am considering buying this ignition kit.
http://www.dynoman.net/ignition/dyna2000.html
DDK1-5C
Ignition and 2.2 ohm standard coils with DW600 Wires

I am just looking for some feedback on this kit, is it worth the 400+?

[TOOLS1]

I still prefer points, and condensers, so I would say NO, but I am sure it is a good ignition system. Why not just change the oil, or replace the coil (whatever). There is a mod where you use GM ignition coils, and I have seen bikes with it done on, and they run great. Somewhere there is a thread on here about it. It was done by "Pinhead". You might want to look it up before dropping $400.00
TOOLS

[Re-run]

Well, since his bike never came with points, that is a moot point.

The dyna systems are good and for the most part, aside from a few of the S models, have always been good.

Cyclex makes an optical system that is a bit cheaper and they usually make good stuff. Out of stock right now but you could give them a call and they might be able to throw 1 together for you.

Besides that, new coils never hurt.

[dietCB750SS]

The main reason that I am leaning towards the dyna is I am unsure of exactly what the problem is with my bike right now. Could a bad coil cause the bike to have power to the indicator lights near the ignition switch even when the key is turned to off?

[TOOLS1]

Two entirely different circuits, so yes if the coil is bad, it will not effect any other systems.
TOOLS

[dietCB750SS]

Maybe I should start looking at this differently what is it on the bike that cuts off the power from the gauges when the key is switch to off?
If I unplug the red plug on the wiring harness that goes to this thing that is pictured, in my first post, everything will come on (with no key in the ignition) and the bike will not start.

[TOOLS1]

The ignition switch/key switch provides power to the gauges when the key is in the "ON" position, and the bike will not start when you unplug the thing in the picture, because those are your ignition triggers.
TOOLS

[dietCB750SS]

I have swapped out the ignition switch, and still, with the switch in the off position the gauges still light up. Is unplugging the ignition triggers what is causing them to light up while in the off position?

[TOOLS1]

The ignition triggers have nothing to do with the gauge lights. When you replaced the switch, are you talking about the part with the key, or the actual switch which is under the part with the key.
For your gauge lights to be on with the switch in the off position, you would have a dead short, or when you installed the key switch, you did not have the two parts orientated correctly to each other.
TOOLS

[dietCB750SS]

The whole thing, and I was getting the same results with the stock, and the new switch

[TOOLS1]

Then you have a dead short, or some wires crossed. I would start by removing the fuses one at a time, and when you see the lights go out, you will know that the problem is in that particular circuit.
TOOLS

[dietCB750SS]

Thank you Tools, your insight is greatly appreciated. I will make sure I post my findings when I get to try this over the weekend

[dietCB750SS]

finally I got a chance to look at the bike, one new development is that the horn button only works if i press both the horn and starter button... wierd. and I tested the rectifier and i didn't get any reading off of it. I checked the manual several times and still no reading so I am assuming it is bad?

[motogrady]

massive headache.........I'd unplug every molex connector, and start from the charging circuit, adding circuit by circuit.  Disconnect the horn, the lights, heck that thing will run on the battery alone with the charging circuit disconnected till the battery drains.  Try that, if you think it's in the charging side, the rectifier,
whatever, see if it all works with that stuff disconnected.

Sounds like you have something crossed, maybe take an evening, download the wiring diagram for your
model, and trace every freaking wire, making sure everything is going where it's supposed to.  Check each
one off with a marker on the diagram as you go.  At least then you'll know it's a faulty part, not 2 wires melted together or a set of molex plugs crossed.

[TOOLS1]

The horn button works by grounding the circuit. Since it only works when the starter button is pushed, I would say that your handle bars are not grounded. Try grounding the handle bars with a test wire, and see what happens.
TOOLS