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Discussion Starter · #1 ·
Problem: Starter engaging with turn of key! Not button!
Bike: 1972 Honda CB450 Twin


So… Glad to be here on the forum- newbie here, and love these old CB Honda’s. First 450 I’ve ever had though.


Let me go back to the beginning before the non-stop starter…

Bike was firing just fine off the starter button, when all of a sudden, it all stopped. The starter button seemed to be dead. Lights were on, gauges were on, etc.
Did some research and thought the culprit might be the ignition/coils/solenoid/starter button itself.
While I was purchasing a NOS ignition, I went ahead and bought some coils & solenoid as well.

Installed all, wires matched up on both the ignition, and the coils- NOS, not aftermarket- Feel pretty confident it was done right.

Turned the key to on, and the starter engages non-stop. As if I’m pushing the button, but I’m not.
The run/stop button has no effect on this- it still engages. But everything in the controls/lights/horn works properly.

Thought it might be something with the starter button. Took the controls apart and connections seem to be good. Button seems to make contact as it should, to "ground" out as it hits.

Thought it might be the solenoid- switched that out- same thing- constant starter with turn of key.

Thought it might be the ignition (even brand new can be bad/wrong sometimes)- switched that out – same problem.

Checked wires throughout for breakage, shorting, etc. in headlight/frame/to controls- All seem to be good.

Questions:
The coils – I've looked at a diagram, and my wires seem to match - 1 black/wht wire off each coils to a singular black/wht wire in harness?
1 double (blue) wire from new coil, split to blue wire on condenser, and blue wire on points?
Other side is same but with yellow wires?
Did I do any of that wrong???

Could it be the starter itself? Stuck? How to diagnose?

Any other thoughts/insight as to what might be making this do this- let me know.

I checked the usual- fuse, my hair, blinker fluid and prayed every time I turned the dang key… but it still engages instantly.
UGH!

Thanks!
 

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Sensei
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Quick two part diagnostic test:
Unplug the Yellow with red stripe wire inside the headlight shell....Does it still roll the engine over when you turn on the key?....IF yes, that wire is shorted to ground somewhere between the headlight shell and the solenoid ,....IF NO, the short is inside the handlebars or at the switch-block.....
OR the solenoid switch contacts are "welded" closed.....To check for this second possibility, unplug the Yellow/red wire at the first connection from the solenoid
 

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The coils are correct; the black/white wire goes to the run/stop switch, the other side of which is a black wire to the key switch. Starter solenoid should have one large wire directly to the positive end of the battery, and another large wire to the starter motor. With an ohmmeter, you should read 12V between those to large terminals when the key is off. The starter solenoid should have two small wires, one black from the key switch, which is 12V when the key is on, and the other a yellow/red wire to the starter button, which should also be 12V with the key on, until you push the starter button. Since the Y/R wire goes through the headlamp, you can disconnect it there and try again; if the starter doesn't run, the wire is shorted, probably where it enters the handlebar. If it still runs, then the short must be between the headlamp and starter solenoid.
 

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Discussion Starter · #4 ·
Thanks for these quick replies all!
Before I went off to work this morning I anxiously tried the quick tests--
Verdict--- when I unplug the yellow/red wire inside the headlight housing, it doesn't engage!!!! So, I'll be searching for that culprit along the bars later today.
Thanks!!!
 

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Discussion Starter · #5 ·
Ok, so... messed around with it a bit more this afternoon. Followed wires, unwrapped just about everything. Nothing seemed to be broken, or causing the opposite when moved around.
Pulled apart the RH controls, for the 100th time, and realized something.
When the upper and lower portions of the controls are pulled apart, the starter doesn't engage. In fact, the button doesn't even work while it's just hanging there. Light switch and everything still works fine. Put them back together on the bars, and the starter engages on key turn again.
That extra wire is now confusing me. But why'd it work just fine with the extra wire in there before???
Anyway, the extra wire is stripped and wrapped around the screw (on the right side) that's holding down the starter button contact (what's that thing called!??). Anyway, pic attached, but I already unwrapped that wire from the screw so it's not in the photo.
controls.jpg

Is that wire causing a problem? It goes from that screw, to a bolt (grounded). Why is it there?
Anyway, remove the wire, and the button still doesn't work. And if I put the upper and lower controls back together, the starter still engages with turn of key...
So that wire is doing nothing I guess.

Kinda at a loss on this one. Must be making some contact when I put the two halves together and shorting out. But the button just seems to not be working as well, regardless.?

**Plastic button pushes the spring in, to create contact of back of button and plate, which has a plate (in photo) holding it down. And there's a wire making contact on the backside of the plate, which is the yellow/red wire.
Correct??

Thanks!
 

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Sensei
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Button pushes a brass pin in through a clearance hole on the retainer....When pin touches the Yellow/red wire contact (on the fibre insulating plate), the brass pin and spring (compressed against the metal retainer) complete the ground link to the housing (which if also grounded through the handlebars, riser and dual ring-terminal wire to the chassis), cause the solenoid to activate, rolling over the starter motor....

It appears to me to be a poor solder job where the Y/R wire attaches to the contact .....Any stray grounding of that bare wire end will activate the solenoid....
 

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Discussion Starter · #7 ·
Ahh, thanks!
So I'm assuming the extra wire then, grounded to the frame, is compensating for the fact that when the aftermarket handlebars were put on, the metal pin which locked/inserted into the bars and probably grounded the control housing, is now ground down/gone. The aftermarket bars also have a thick coating on them.
So, I need to make sure there is a good ground/contact happening, so that when the button goes through that cycle, the housing is in fact doing its "contact" job.
Probably the reason it's the opposite and the starter is engaging instantly when the key is turned, and not even giving that button a chance to go through that electrical cycle you mentioned.

And- if the solder job is bad- I'll just redo that as well.
Thanks!
 

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Discussion Starter · #8 ·
Re-soldered yellow/red wire to back of button plate. Sanded down black coated handlebars so metal was touching inside of controls, all the way around.
Works perfectly.
Case closed.

*prior, it was working because there was just enough black coating scraped off for the inside of the control housing to be touching metal. Combined with possibly a bad soldering job--- it was luck that it even was working. I must have moved the controls just enough to lose contact with that bare metal.
 
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