Sudden engine cut outs

[Lobo]

Given both the Kill Switch and the Start button are failing it might just be the multi-connector - can’t remember if it’s found within the headlamp or boot below the tank?

Do the headlamp / park lamp behave 100% as these too share the same multi connector?

Have a look at this wiring diagram, and note the three black (ie switched live) feeds all originate from a common multi-connector.

[Athame57]

Given both the Kill Switch and the Start button are failing it might just be the multi-connector

My kill switch works fine... I'll still go have a look at the multi-connector though. 

[Lobo]

Sorry - misunderstood the bit about starter button / kill switch.

I guess the easiest way to check is to have the engine running whilst moving the under tank connections boot up & down a bit in the hopes of a cut-out. (or within the headlamp bowl wherever…)

[Oddjob]

Won't be a block connector if the wires go through the bars, it will be multiple individual connectors. However the black connector could still be the common factor.

[TrickyMicky]

I had a problem with the main beam warning and indicator warning lights on the handlebar display. It turned out to be where all the earth wires joined inside the headlamp. 40-odd year old bullet connectors were quire heavily tarnished meaning that the earth current tracked through whatever route possible. Our bikes might be old, but at least we can access all the individual wires and connections, and with a little patience they clean up quite well.  The other similar problem I had, which caused a lot of head scratching, was the main fuse failing quite often. It turned out to be the multi connector behind the fuse carrier, upon unplugging it all the connections inside it were a nice green colour!! Apparently if a fuse "blows" in the middle of the glass then it's a short circuit, but in my case the end caps of the fuse were falling off through overheating, caused by current having difficulty being drawn through the poor connection. 30 minutes work with a set of jewellers' files cured it. Be lucky. Mike.

[McCabe-Thiele (Ted)]

For removing green contact corrosion I followed Julie's tip & used Cillit Bang Limescale remover. A squirt on the stuff on the contacts then a few minutes later it just came off revealing shiny brass spade terminals. Even used on the voltage regulator spades.

Updated: I used an old toothbrush afterwards & rinsed with WD40.

[Athame57]

For removing green contact corrosion I followed Julie's tip & used Cillit Bang Limescale remover. A squirt on the stuff on the contacts then a few minutes later it just came off revealing shiny brass spade terminals.

At that price I'll order some anyway! 

[Cappodimonte]

Have sorted your cut out problem yet or are you still working on it ?, having re read the topic it could be so small as to be a ‘Dry joint’ where wires are soldered to a switchgear of motherboard, it would initially work but electrical resistance builds up and bingo stoppage. It’s a bit like a skybox that goes static, you turn it off, wait ten seconds and switch on, hey presto it works again. Think I’d have another look at the internals of the kill switch, after all the bits are 40+ years old.

[Athame57]

Have sorted your cut out problem yet or are you still working on it ?

I got a new battery from DSS, a mainenance free gel one. Easier starting now and no cut outs on the move. There remains an issue of the starter button sometimes failing to work unless I give it a go with the kill switch on, then back to normal. I opened the unit but can't see anything obvious.