The bike starts off the button (eventually) when left overnight and the battery as its absolutely best charge in it off the Optimate. Full 12.999999v.
After 5 mins idling it won't turn over at all. Sounds like a flat battery etc etc etc.
So I popped a plug out - I have to fix the carbs anyway - and turned it over.
The spark was tiny, less than 1mm.
I popped the connectors off the back of the HT coil and attached a multimeter ..
Its getting 0.1v on the ignition and a max of 3.4v when turned over
The other side, the left side, 9.0v steady on ignition dropping to 4v on turn over.
Verdict? Somewhere between the battery and the plug, the loom is loosing 3-4v and on the right hand side 11.9v.
Verdict? Something in the starter circuit is absolutely fecked.
Anyone want to be more technical?
I suspect the idea that the main live is corroded/mullered somewhere in the loom is bang on.