Honda GX390 not turning off with key

[AHPP]

Honda GX390 on my Opico Skidster. Took the key start box off to get the fuel tank off. Cleaned tank, back together, starts on the key as normal, runs fine. Doesn’t turn off with the key. Googled it. Prime suspect some wire under the tank that goes to the magneto. Pulled tank back off, recoil and engine cover off, all looks in order. Switch box apart. All looks in order. Cleaned various contacts, scraped paint from inside of holes in frame where key box mounts. No joy.

 

Suggestions?

[AHPP]

Annoyingly I’ve fixed it but don’t know how. I just put it back together again and it works. Obviously I also stripped a thread in aluminium while at it.

Ideas about initial issue still gladly received.

[Stubby]

1 hour ago, AHPP said:

Annoyingly I’ve fixed it but don’t know how. I just put it back together again and it works. Obviously I also stripped a thread in aluminium while at it.

Ideas about initial issue still gladly received.

The ground wire going to , well , ground ?

[Macpherson]

+ 1 for disturbed earth or moved / cleaned bad connection 

[AHPP]

It’s always a bad earth isn’t it but the only thing I disconnected that I could identify as an earth was a black wire between the digital hour counter and the switchbox/frame and I cleaned that the first time. Maybe just not that well? Who knows.
Something I’ve always associated with machine ownership is the ability to accept that these things are sometimes just a mystery and not get too stressed about them. Whenever confronted by mechanical annoyance, I like to imagine aspen Bob dutifully and stoically traipsing round his yard, fixing things that his men have fecklessly rolled down a hill twice that month. My bad earths seem less bad.

[Stubby]

1 hour ago, AHPP said:

It’s always a bad earth isn’t it but the only thing I disconnected that I could identify as an earth was a black wire between the digital hour counter and the switchbox/frame and I cleaned that the first time. Maybe just not that well? Who knows.
Something I’ve always associated with machine ownership is the ability to accept that these things are sometimes just a mystery and not get too stressed about them. Whenever confronted by mechanical annoyance, I like to imagine aspen Bob dutifully and stoically traipsing round his yard, fixing things that his men have fecklessly rolled down a hill twice that month. My bad earths seem less bad.

It will be the wire that comes from the switch that shorts the spark to earth I would think .

[AHPP]

It will be the wire that comes from the switch that shorts the spark to earth I would think .

That one only went to the hour meter up the top right of the machine. The spark plug is bottom left. Totally different loom going down that way. Maybe I’ll find out tomorrow when the problem returns and I have to actually fix it.  

EDIT: Just read that again. What you said does make more sense than what I said. It’s been a long evening and I didn’t know a lot about electrics before I piled my way through a lovely little bottle of sloe vodka.

ANOTHER EDIT: The hour clock turns off when the engine turns off, fairly firmly supporting your hypothesis.