Yamaha V50M moped won't turn off with the key!

[Pablo V50]

Hello all

I've just received back the very V50M I used to use when I was 16 - I'm 51 now!  It was my mums before she could drive, then my dad's commuter, then I used it to do my paper round on and then my brother used it when I could drive.  It sat in my dad's garage for about 25 years before giving it to a friend's son.  After more years, friend's son now works for Triumph testing new bikes on track in Spain so poor V50 now a tad overlooked.  Anyway, I was asked if I wanted it back as a resto project.  Yippee - time to revisit my 16 year old self.

So, I've been doing a bit of a "rolling restoration" on it - not much point spending too much time and money if it's knackered.  Some success and it's running now, but I've got a bit of an electrical problem that is driving me nuts.  Basically you can start the moped without the key and when it's running (with or without the key) the key won't turn it off.  The ignition switch is working as the neutral light comes on and the key turns the running light and headlight on and all other electrics work fine.  I've tried to decipher the manual wiring diagram and fumble about with my multi-meter but I'm not sure what to test or to look for.  Any help from you guys would be very much appreciated.  I have seen another chap has restored the exact same bike on here and it looks great.  Here is a picture - it was a green version until friend's son painted it grey.

[Snakebite68]

Bearing in mind that I don't have a clue about electrics, but do know a bit about locks in general...
I'm suspicious that the ignition barrel may be failing, it's probably had a LOT of wear over the years.

[Pablo V50]

Thanks Snakebite.

The ignition barrel is fine though, a little loose from wear but the key turns the ignition switch.

Stripped it all down again this morning but no joy!

[Cynic]

Have sent a pm, 

Don't like posting ignition related info in open forum.

[Pablo V50]

On 5/8/2022 at 3:01 PM, Pablo V50 said:

Hello all

I've just received back the very V50M I used to use when I was 16 - I'm 51 now!  It was my mums before she could drive, then my dad's commuter, then I used it to do my paper round on and then my brother used it when I could drive.  It sat in my dad's garage for about 25 years before giving it to a friend's son.  After more years, friend's son now works for Triumph testing new bikes on track in Spain so poor V50 now a tad overlooked.  Anyway, I was asked if I wanted it back as a resto project.  Yippee - time to revisit my 16 year old self.

So, I've been doing a bit of a "rolling restoration" on it - not much point spending too much time and money if it's knackered.  Some success and it's running now, but I've got a bit of an electrical problem that is driving me nuts.  Basically you can start the moped without the key and when it's running (with or without the key) the key won't turn it off.  The ignition switch is working as the neutral light comes on and the key turns the running light and headlight on and all other electrics work fine.  I've tried to decipher the manual wiring diagram and fumble about with my multi-meter but I'm not sure what to test or to look for.  Any help from you guys would be very much appreciated.  I have seen another chap has restored the exact same bike on here and it looks great.  Here is a picture - it was a green version until friend's son painted it grey.

Thanks for the replies to this post.

I found the fault over the weekend.  It was indeed the earth circuit that was the problem.  I know that the earth circuit should be open when the ignition was on and closed (i.e. making a circuit to ground) when the ignition was off.  I tested the continuity of the black and black and white cables for this circuit across their terminals in the ignition switch and they were fine.

I then traced the back and white and black wires through the loom to a point in the battery compartment and saw there were two cable junctions between black and black and white cables there.  Knowing that I had disconnected the cables when I took the engine out to transport the bike, I wondered if I had reconnected these wires incorrectly and the black should join with the black and white and vice versa.  So more out of desperation than anything, I switched the wires around connecting the black to the black and white.  Hey presto!  it worked.  I don't know if this is how a bike earth wiring loom should be connected, because it doesn't seem logical to me, but anyway, I'm happy now and its all working.

[Snakebite68]

Grats!