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CB750K Sidestand mod?

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K2-K6:
I can see your reasoning Simon, I clipped the detail from a Kawasaki forum as thought it was very clear schematic of this arrangement and looked to be from one of their manuals.

It does get convoluted though as most neutral switches are effectively faill safe by removing contact to earth when moved away from that home position and so needing no constant contact to keep the light out. Obviously not an engine stopping circuit original, but then piggybacking something else onto that mechanical logic to make such a device.

On relay powered down status, I believe most fuel injection pumps are relay " powered to on" type when called by ecu, giving a failed state of no fuel pressure with the same consequence of engine stop that you've observed there.  The relay seem to be very reliable and I've only experience of two failing in years, one on audi car at 139,000 miles and one on Land Rover at 157,000 miles. Quite possibly a case for planned replacing during maintenance and both Bosch relay. Nothing to moan about in service life in practice though. It's often this route that is toggled in older alarm system when added as supplimentary kit too, think modern is built-in to ecu more now and logic controls of injection pulse output completes this function.
Certainly seen more failures in total of ignition barrel contact on bikes over similar period of time but much less miles recorded. 

All of these ultimately balanced against what you are trying to prevent from happening by stopping errors will have acknowledged level of probability in occurrence to deal with in some form or another.

Lobo:
Steve, when I wrote starter motor inhibit I meant that the starter wouldn’t spin; your post suggests it did, but the spark was inhibited???

I guess Bryan, my personal idea of fail safe (in this very specific case) is that the engine keeps running should any component of the sub-circuit or it’s wiring fail.. whether open or closed circuit.

Nige, I did not intend to concentrate on the relay, but rather the whole sub-circuit, meaning failures of the sub-loom, it’s earthing, it’s connections, the 2 switches and indeed the relay itself would allow the engine to stay running.

Fuel injectors circuits carry a different set of risks in that fuel is being pressurised - although I do see differing points-of-view wrt ‘what is safest’ - especially so in that it will vary iaw the threat. (as indeed you touched upon)

A very interesting topic tbh, and shows how one just can’t sit down and design a circuit without a fair amount of understanding the problem.  It must constantly lead to ‘doh, I never thought of that’, type frustrations!

SteveD CB500K0:
Correct.

It’s like trying to start up with the kill switch engaged


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K2-K6:
"A very interesting topic tbh, and shows how one just can’t sit down and design a circuit without a fair amount of understanding the problem.  It must constantly lead to ‘doh, I never thought of that’, type frustrations!"

Definitely and often not realised just how much of this element in many products prior to anyone seeing them.

Your original reference Simon to familiar risk and protocols in your industry obviously have very pronounced end case scenario in the event of failure which may not be so readily apparent in this case. Thinking it through I was wondering whether to include the following story to bring wider view.
Not keen to project uncoroborated/dramatic events, this though is direct from a good friend and very experienced rider. Travelling across Europe had stopped at top of a mountain pass, setting off again downhill and turned right out of carpark (the Europe part has significance here) gentle run downward and approaches a left hand hairpin, sidestand still down!!! It hit the road and fired him and bike straight into a peripheral retaining wall outside of corner with that contact, no more than 30mph too. The injuries were serious as the bike pummelled him into the wall with consequently broken pelvis leg etc. The bike was a goldwing. It resulted in hospital, repatriation, recovery and longer lasting effects. He felt lucky it wasn't even more serious  :) 
Again the European part has an impact, if he was driving on the "right" side of the road  :) (Micheal Cane reference here) it could push the accident directly into oncoming vehicles. 
This bike had that rubber piece missing (it's no fault of the bike, just his own acknowledged cause of not fitting a new rubber part) when it should have been there,  but even with a sidestand orientated to flick up with that rubber it effectively fired him and bike straight into the accident, a very sobering tale.
Must admit when these devices and control first started appearing I thought they were a bit nimby-pamby and "why would you need that" type of thing. Guess that the manufacturers were seeing much more of this type of thing and set about answering to reduce their customer risk. Easy in hindsight to now see an overall picture. 
Certainly anything you can competently do to reduce risk in this scenario has high value personally I feel. I saw someone at a bike meet with a rubber wedge door stop and "remove before flight" red tag on in just wedged between the clocks that the rider took out and put inside his jacket after folding the stand, he a self confessed habitual leaver of sidestand down. Cheap and practical at least.

SteveW:
How about something really simple such as if the side stand is down and the ignition is on all the idiot lights flash?

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