Topic: Help please: ignition lights cutout

[1977_cb550k]

1977 CB550 - problem; no ignition light when key turned on.

I’m on a 3-day ride with mates and after a fuel stop I couldn't start the bike. The ignition light wouldn’t come on when I turned the key. Battery is fine, fuses are fine. Finally traced it back to the rectangular plastic wiring harness behind the ignition switch in the steering column.   The harness needs to be lifted up to keep an electrical connection, so I’ve used cable ties to hold it up to get going. It’s holding up ok but isn’t a reliable fix.

I need to sort it out and am wondering what are the common issues with these ignition wires/harnesses?

The fork springs were recently replaced so I imagine the mechanic has changed the various cable positions during reassembly etc which has resulted in the harness somehow disconnecting.

Any tips?

Also, is the best path to take a look at the harness/wires to remove the headlight and go in that way?

[newday777]

'Finally traced it back to the rectangular plastic wiring harness behind the ignition switch in the steering column'

Are you talking about the white plastic base of the switch that the harness connector plugs into the switch?

[BenelliSEI]

Those switches do wear out and fall apart internally. “Lifting” the harness may be masking an internal problem, or you may just have a loose connection. Remove the headlight, unbolt the “pot” and it should fall away far enough forward to allow access to the bottom connection. Pull the switch out where you can have a look and determine the problem. From memory I think there are only a couple of bolts holding it in, from below?

My ‘78 550K had a very similar problem. I remember taking the switch apart, spotting the issue, but in the end a new switch was the only fix.......

[RAFster122s]

If the plastic housing that holds the switch together breaks a tab, then the connections usually break. Do not know of anyone selling the plastic housing separately or 3D printing a replacement.

[bryanj]

Emgo do 2 different switch bases, depends how many contacts in there

[1977_cb550k]

Yes Stu, the white plastic harness. 

It looks in good condition so must be an internal connection issue. I’ll need to get in there to take a look.

[1977_cb550k]

Thanks Benelli for confirming how to get in there. Will drop into a workshop today on our road-trip. 

[RAFster122s]

Hopefully your switch isn't falling apart, a big cear bag or bag around the switch bottom might catch the ball bearing in the switch assembly if you pop off the switch from the lock assembly and the switch ball bearing is loose. Finding it if it drops out could be a pita if on concrete and it goes bouncing away...
Had an issue on my CX where the plastic clip on housing that retains the switch broke the one of the tabs and it didn't hold the switch in tight allowing it to break connection. Total pain to diagnose as it has charged battery and fuses were fine. A tab finger had cracked when I cleaned the switch and failed later.  Wasn't tough to find, just a pain as the CX switch was in the maggot headlight cowl which isn't a tiny job to remove to gain access to the area.

Good luck sorting it out.
Some guys have used some strong zip ties around the lock body and across the bottom as temporary fixes when this happens. Tough to get it to not slide down with any vibration... definitely a temporary job.

[BenelliSEI]

The Emgo switches don’t have the best reputation, but I’ve had one on my K8 for years and it seems OK. Fairly reasonable price.

[RAFster122s]

One weakness is fatigue on the switch from the harness pulling on it. A few of the switches that suffer from it have an optional improved switch that has a wiring pigtail with external connector not in the electrical switch available.
Another failure mode is excess current through the switch and adding a relay to the main switch allows you to bypass this failure by routing that heavy current flow through the relay contacts.

[1977_cb550k]

Thanks everyone for all the help. Very helpful advice.

Turns out it was the ignition block itself. The contacts on the back that connect to the harness were corroded and needed to be welded back - it’s a temporary measure but will get me home.

So now the follow-on question. Where do you recommend getting a new ignition from? And any brands to avoid? I’d prefer to get NOS if possible?

[bryanj]

Honda is best but sit down before you check price.
Go to cmsnl and look up your exact model, they do vary, the put the part number into google to see who has one in stock.
The white block on the loom is not available seperately by the way

[newday777]

Thanks everyone for all the help. Very helpful advice.

Turns out it was the ignition block itself. The contacts on the back that connect to the harness were corroded and needed to be welded back - it’s a temporary measure but will get me home.

So now the follow-on question. Where do you recommend getting a new ignition from? And any brands to avoid? I’d prefer to get NOS if possible?

Good that you got it fixed.

If at all possible get one from Honda.
The ignition lock set(includes seat lock) part number is
35010-377-007.

South Sound Honda in Washington State USA shows it's available so try your local dealers and if they say it isn't available from the warehouse, have them do a dealer search to see if there is one that has one in inventory.

#4 and #5 on the fiche
35010-377-007

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB550KA_(77)_550_FOUR_K%2c_JPN%2c_VIN%23_CB550K-2000007_TO_CB550K-2015308/SPEEDOMETER_%2b_TACHOMETER_%2b_PILOT_LAMP/e78b9119-f792-4cf6-ab47-c471041bb569/5bc643e9-e710-469f-ac7a-4c9f79648eac/y

[newday777]

You can also check the superceded numbers as some dealers have old NOS parts on the shelf still as well as ebay parts sellers

*This part replaces 35010-410-000 *

*This part replaces 35010-393-771 *

*This part replaces 35010-393-770 *

[1977_cb550k]

Once again the SOHC4 come through with great info! Thanks everyone, absolutely legends. Really appreciate your help, knowledge and advice 👍