Honda-SOHC

SOHC.co.uk Forums => CB750 => Topic started by: Gmac on December 07, 2024, 01:32:03 PM

Title: Lights not working
Post by: Gmac on December 07, 2024, 01:32:03 PM
Just picked up a really nice '74 K4.

Seems to be mostly original, and most things work, except the head and tail lights, which was a surprise, given the overall condition of the bike, which I'd say is excellent

The switch illuminates the clocks, and the brake light works

Any obvious things to check on these, as it's my first CB750
Title: Re: Lights not working
Post by: SteveW on December 07, 2024, 01:38:42 PM
I’d start with the fuses.
Title: Re: Lights not working
Post by: Gmac on December 07, 2024, 01:48:43 PM
Quote from: SteveW on December 07, 2024, 01:38:42 PM
I’d start with the fuses.

I will do that. I just wondered if there was a 'go to' for this issue.

I don't have a wiring diagram, or manual, so going to have to work through them
Title: Re: Lights not working
Post by: Nurse Julie on December 07, 2024, 01:56:31 PM
Check fuse, bulbs and connections, in that order. All books and publications you need are in this link Guy. You can download and print them as well.
https://info.sohc.co.uk/
Title: Re: Lights not working
Post by: Gmac on December 07, 2024, 02:22:04 PM
Quote from: Nurse Julie on December 07, 2024, 01:56:31 PM
Check fuse, bulbs and connections, in that order. All books and publications you need are in this link Guy. You can download and print them as well.
https://info.sohc.co.uk/

Many thanks  :)
Title: Re: Lights not working
Post by: Mike_Berkshire on December 09, 2024, 09:53:11 PM
I had a similar issue on my 76 K2. It was corrosion between fuse and fuse clip
Title: Re: Lights not working
Post by: ST1100 on December 10, 2024, 07:38:11 AM
I'd trace & confirm with a multi-meter...
On a CX500 I'd worked on the fuses showed visually intact melting wires inside the glass, but no continuity...
Title: Re: Lights not working
Post by: Skoti on December 10, 2024, 08:50:32 AM
Quote from: ST1100 on December 10, 2024, 07:38:11 AM
I'd trace & confirm with a multi-meter...
On a CX500 I'd worked on the fuses showed visually intact melting wires inside the glass, but no continuity...

Aye,

good advice above.


Had a problem with my F1 electrics,  bike stopped on the road, checked the fuses and all looked OK.

But eventually discovered the wire in the main fuse had melted through inside the end of the metal cap, and only at one side where you don't notice with just a quick visual inspection.

Anyhow later learned that this is often the case when you have poor intermittent connections through corrosion etc, and then just enough heat builds up to damage the fuse in this way.

Corrosion in the main engine block connector caused the issue for me.


Good luck

Skoti
 
Title: Re: Lights not working
Post by: Gmac on December 11, 2024, 05:18:26 PM
There are signs of corrosion on some of the wires and connectors.

I plan to go through them, and replace some connectors, when I get the chance
Title: Re: Lights not working
Post by: Gmac on January 06, 2025, 10:57:16 AM
It was just the main 5a headlight fuse. Luckily the original spare was still in it's holder. All sorted, and everything working now