Topic: CB750 Ignition problem

[nanahan]

Hey guys!

So I have a 1976 CB750K.
Today i went riding, and after 30 minutes of riding, the motorcycle just shut off on me on the freeway.
I have an app that tells me the condition of my battery, the voltage was good above 13 volts.
I tried to turn it on again but  get nothing, the motor wouldnt turn.
I then switch the ignition from ignition to Accesories.
The motorcycle started with no problem.

I went over all the cables and connections. All of them looked good, no burnt wires.

Could it be my ignition switch?


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[Mr Freeze]

Sounds like it. The connector block for the ignition switch often gets burnt or could be the switch itself.

[BenelliSEI]

Your ignition switch has three positions: OFF-IGNITION-PARK. It should only run in the middle position. The third spot is for parking, leaving the tail light on (it’s the law somewhere!) and allows for key removal. If you can ride in the third position, get a new switch fast. It’s failing.....

[nanahan]

So I just installed the new ignition switch. I have the same problem, when i turn the key to ignition and try to start the motorcycle, the headlight turns on but the motorcycle wont turn. When i turn the key to park, the motorcycle turns on (before the incident i was able to turn on the motorcycle in park).

Any suggestions?


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[robvangulik]

Switched wires...

[nanahan]

I don’t think is that, like I said before, I was able to turn on the motorcycle in park and in ON, t only difference was that in the ON position the headlight would turn on.
Now when I then the key to ON the headlight does turn on but can’t start the motorcycle.


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[bryanj]

Please clarify do you mean wont start or wont turn over on starter

[nanahan]

SOLUTION.

So I started checking all the electric components and found two fuses where blown.
Smh. I could’ve sworn that was one of the fir things I checked, but I guess not.

But now I have another problem, I have a battery app tracker thing, and when I took the bike for a spin and cane back home, the battery was not charging to a near 100%
The battery was slowly draining, I did notice the break light was dim and dimming as the motorcycle was idling, and when I would accelerate the light would shine brother.

Could it be a cable grounding?


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[BenelliSEI]

With due respect to your phone app, doesn’t sound any different than my CB750. At idle there is no real charging going on. Rev it up, and the lights will brighten (good sign, it’s charging). With a volt meter, check your battery voltage in the morning. Go for a ride, then check it again, after everything cools down. You can also check the voltage when idling, and reving it up. You can see the voltage rising.

[nanahan]

SOLUTION

Yet again, while going through all the connectors and cables i found that a ground wire connected to the front break switch was loose. The moment i connected it again i started seeing the battery being charged.


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[pjlogue]

You should go through all your ground points and make sure they are clean to bare metal and tight.  If you have issues with electrical connections it is a good bet where you see one problem there are three more you don't know about.  I would suggest you systematically go through every single bullet connector, spade connector, ground points and especially the 3 phase yellow wires connectors coming from the alternator and the fuse contacts where the fuse sit in the spring metal block.  It may seem like a big job, which it is, but you will be forever chasing electrical problems if you don't go through the entire bike.

-P.

[bryanj]

There is no ground on the front brake light switch and moving those wires cannot affect charging rate UNLESS in moving them you moved other wires in the headlamp shell

[robvangulik]

It is just a switch, which only makes contact when brakepressure is applied.
 I don't see how that would affect charging.

[nanahan]

Yeah i don’t know how but yeah the green end was loose, once I fixed it the motorcycle was charging the battery even on idle.


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[BenelliSEI]

See what Bryanj said, +1. Nothing even remotely linked to your charging system. Keep looking.