Hi,
I'd appreciate some tips on how to go about diagnosing this one.
Brief history. I bought the bike in January. It had been sitting in someone's garage unused for more than two years and needed a new battery, fork seals and carburettor clean, but otherwise was in good condition. Not relevant here, but the compression is not great and I assume rings, which I'll have a look at later. Has been running well, except for a non-start after I left the bike in the garage unused for two months over winter. I charged the battery and all was well, battery voltage and charging voltage both good. That was about six weeks ago.
I went for a ride yesterday afternoon and moving off from a light all electrics cut out and the bike stalled. It was like the battery had been disconnected. I checked the fuse, which was good, but swapped in the spare anyway, which made no difference. After getting it home, I took a multimeter to the battery, which showed 11.3 V. I suspected a USB port I installed a couple of weeks ago, so I disconnected that and charged the battery overnight. The battery is now showing 13.3 V, but the electrics are still dead, by which I mean that nothing happens if you turn the ignition key on. I disconnected the negative lead to the battery and tested voltage from the negative battery terminal to the disconnected negative battery lead, which showed 9.3 V. Does that mean a short or parasitic draw somewhere? I can't find any bad wiring or connections with a visual inspection.
I don't know what to do next. Ignition switch? If so, how best to test that?
I had a look at the wiring diagram and decided that this has to be the starter relay solenoid. I'll go to the bike shop this afternoon and get another one and see if that works and will post the results in case it helps someone else.
Yes. Starter relay. The positive lead from the battery routes through this and if it fails (at least how mine did) the entire electrical system goes dead, as though the fuse had blown. New one solved the problem. Given its tiny size and importance, this seems like a good inclusion in the on board spares kit.