Topic: Wiring question. Bike tries to start when I pull clutch with key on

[junruh]

Been working with my electric start. The PO had put on a push button beside the frame, disconnected it, I want to fix it right. I turn the key on, pull the clutch and it instantly tries to fire up. Not sure if some kinda way the starter relay is bypassed? Black wire shown is constant hot when key is on. That and a green wire with red stripe are hooked to the control power for the starter solenoid. Do I have a messed up safety? The starter button doesn’t work either. Another thing that I’m not sure on how it’s supposed to work. The run switch and the on/off switch on the RH bar don’t stop it from cranking.
EDIT- Sorry totally forgot to list my bike. 1975 Honda CB550F.

[scottly]

What bike? The starter wiring changed over the years. The handlebar switch only kills the ignition (spark). The black wire is connected to a red wire that is connected to a blue wire: where does that wire go?

[junruh]

Sorry! See edit for bike model. Blue is just an insulator covering a yellow wire with red stripe that goes to the starter solenoid. The push button switch I removed was just in between the black and red that I now have tied together. Pic of old switch is shown as well, you can see the red and black under the frame and the other pic is how it was tied in at the solenoid end.

[junruh]

Switch pic

[scottly]

Blue is just an insulator covering a yellow wire with red stripe that goes to the starter solenoid.

The yellow/red solenoid wire should be plugged into the yellow/red wire that's hanging loose. Who knows what else got hacked?? Where does that added black wire get it's power from? I think I would remove it..

[newday777]

Welcome aboard the forum junruh
1st off, the black, (which is always hot on these bikes) should not be wired to the green/red(red stripe). The green/red is part of the clutch safety switch at the clutch lever. That is why your bike spins the starter when you pull the clutch lever.
You need to sort out your wires from being connected to any mismatched colors. Honda harnesses connect to the same colors at any connection point (there are a few odd mixes of colors on the 75/76 bikes, but not in the starting circuit)
Do you have the workshop manual with the correct wire harness diagram for your bike?
You say you have a 1975 CB550F, but is it the Supersport or the K model CB550? 1975 was the first year of the F Supersport and some put the F as a shortcut for the word "four". There are some differences in the wire harness of the K and the F(Supersport) bikes.
You haven't shown a complete picture in any introduction of your bike nor included the complete vin numbers or steering neck vin plate for us to see the exact model you have so that is why I've written this.
My 550 repair manual and my copy of Mark Paris' CB500/550 restoration book is down in my shop to post any pictures or to look at the wiring diagram to go any further at this point.

To see the difference in the 2 models of the 1975 CB550

1975 CB550F Supersport with stock 4into1 exhaust
https://www.motorcyclespecs.co.za/model/Honda/honda_cb550_super_sport_75.html

1975 CB550K with the stock 4into4 exhaust

[scottly]

Stu, please stop badgering the newbies. I mean, asking for VIN numbers??? The guy is trying to figure out how to un-hack his wiring system, not tell his life story.

[scottly]

1st off, the black, (which is always hot on these bikes) should not be wired to the green/red(red stripe).

He never said the added black wire was connected to the green/red wire, he said the added black wire was connected to the yellow/red solenoid wire....

[junruh]

VIN is attached. Do I need to check to make sure that I have voltage at the yellow/red wire coming from the handlebars?That should be constant voltage with key on correct?

[scottly]

VIN is attached. Do I need to check to make sure that I have voltage at the yellow/red wire coming from the handlebars?That should be constant voltage with key on correct?

No, there should only be 12v with the key on and the starter button pressed, if the button is working. Since it appears the previous owner wisely chose to keep the Starter Motor Safety Unit wiring, the starter will only operate if the key is on, the clutch is pulled in and/or the trans is in neutral, and the button is pressed. It appears the PO bypassed only the starter button itself.
BTW, I don't give a f**k about your VIN..

[HondaMan]

I'm not sure how much this might help, as it looks like some of the wiring is hacked up, but...The Yel/Red wire supplies power to the solenoid from the START button when it is pressed. There is a Grn/Red wire on the other terminal of the solenoid that (on the "F" bikes) went to a safety circuit that required the clutch to be pulled in, or the engine to be in Neutral (or both). The diode that comprises this 'safety' circuit ground is that black thingie that is plugged into that rubber plug that is mounted on the bracket at the bottom right of the 1st photo you have above (first post). You'll find the Grn/Red wire on one side of that mounted plug (the diode part unplugs from it, it's a separate part).

If the safety circuit has been removed/changed then that diode thingie may not be working anymore. In Honda's earlier bike, the Grn/Red wire was just a Green (ground) wire, and you didn't have to pull in the clutch or find Neutral to make the starter work. Apparently, Honda thought that was dangerous enough to make you either find Neutral yourself (not handy in traffic) or pull in the clutch (instead) to enable the START button to work.

All this said: the START button in these bikes has 3 wires tied to it: one is the Yel/Red you already know and love, one is a Black (Power) wire (from inside the headlight bucket), and the 3rd one powers the headlight from the Black wire when the START button is NOT pressed (this make the headlight turn OFF while starting with the button). If the PO installed a high-powered headlamp into the headlight, that melted the START switch inside the handlebar, so then the Yel/Red wire doesn't get any power when the START button gets pressed. So, it sounds like he tried to make some other sort of START button up after that?

You can get new handlebar switches, from places like PartsNmore.com or their USA (Florida) branch at VintageCB750.com. They work well, I just installed some on a CB550K1.

[bryanj]

You say the black and red wire went to the extra switch and you connected them together, that means that you have connected the solenoid to power all the time so of course it starts as soon as clutch pulled with key on as saftey cidcuit is in ground side, also means starter will operate every time lever pulled with engine running which is not good

[jmelche2]

The clutch switch is improperly wired in the headlight bucket (maybe this was already stated).  The purpose of this switch is to allow the bike to start while in gear, not to start the bike when the clutch is pulled.  This has to be corrected as will as the other issues outside the bucket. 

I just replaced this switch on my '74, this has to be wired to the corresponding colors within the bucket. 

[junruh]

Thanks a lot for all the info! Y’all are great! Did a quick check over lunch break. I have voltage at yellow and red wire now when start button is pushed. when I pull clutch and press start button I hear a hum and click. Does this mean I have a bad connection between clutch safety switch  and solenoid or what?

[scottly]

How much voltage do you have on the yellow/red wire when the button is pressed? How much when the button is pressed and the clutch is pulled in?

[Don R]

 Usually, the reason for the added switch is that the original start switch has failed when the cage holding the contacts breaks. I think those started in 75, it turns the headlight off when the starter cranks.

[scottly]

Has the battery been run down from all the testing?

[junruh]

Battery has run down just a little. battery had 11 V and I had 9 V when the start switch was pushed in. Didnt check when clutch and switch were both on. Probably should recharge next? Seems like it maybe would do more than just a little hum with that much voltage but maybe not.

[scottly]

Battery has run down just a little. battery had 11 V and I had 9 V when the start switch was pushed in. Didnt check when clutch and switch were both on. Probably should recharge next? Seems like it maybe would do more than just a little hum with that much voltage but maybe not.

Yes, the battery needs to be recharged. Do that and report back.

[junruh]

Yaaa buddy! That’s got it! Thanks a lot. One more question… are these two wires supposed to be connected? The one coming from the main harness is hot with the key on. I was just reading another discussion about some reg/rec wiring but wanted to make sure before I screw something up.

[scottly]

The black wire up above was the one that went to the added start switch, correct? It looks like it was also added and isn't stock. You could unwrap the tape and remove it, or just make sure the end is insulated and the wire can't short to ground.
The lower one looks like it is for a non-stock regulator/rectifier, and should be connected to a black harness wire, like the reg white wire is plugged into, and the reg white wire should be plugged into a white harness wire. Does the charging system work the way the wiring is now?

[junruh]

Ok I think I’ll cap it. I’ll just have to wait to drive the bike and see. That’s all for right now then. Thanks again! I’m on Cummins forum (my first gen is in the back of a couple of those pics- she’s where most of my little bit of automotive experience comes from) and those guys aren’t quite as snappy as y’all on replies and info. Y’all are awesome thanks.

[junruh]

Well I’m back. It worked for a bit and suddenly now it’s not. Kick start still works. I have 12.6 V on the hot side of starter solenoid. Yel/red has 10.6 with start button pushed. Pulled clutch and pushed start button, no voltage at left post on solenoid. I have no power at any time on green/red wire. What do I check next?

[bryanj]

You can not scatter gun tests with an electrical problem jou must start at the begining and work methodically, jump a test and you may as well not have bothered

[scottly]

Yel/red has 10.6 with start button pushed.

Is the battery run down again? What is the voltage at the battery with the key on, and then what is the battery voltage when you press the starter button with the clutch pulled?