Just in the last few days (not ridden much) someone odd happened.
Few days ago, went for a 30 mile run, came back, stopped the bike, then tried to restart again (seconds later) Would not start, as if battery flat. Just about turned over a few times and gave up.
Odd, I thought. Never done that before in the few weeks I've had the bike.
(Still enough power to power headlight etc)
Took battery out and put it on my VERY slow trickle charger (the type that you can leave the battery on ALL the time (over winter if needed)
Anyway, I left it on for 2 days, the charger light went off, meaning battery full.
Put battery in bike, WROOOM, started instantly

Went for about a 20 mile run, came back, parked bike in garage overnight.
Next day, got ready to go out, pressed starter. Battery almost dead again!
Ehhhhh? What's going on? Battery was charged up, then nice run = it should be all tip top and raring to go.
The only thing I've done to the bike recently was change rear sprocket (nothing to do with battery)
Put the clipons back on (may a wire have got pulled out)
And cleaned with engine cleaner and water around the engine sides and around the starter motor (split in rubber cover on the connector)
I did wonder if these was damp/corrosion on the connection to the starter motor. So had the connector off, cleaned all the contacts and back together again.
I'm just thinking it must be something I've done whilst cleaning (or pulled out when fiddling getting clipons back on)
Though, the clipons were changed over for a week and all was ok. It's just since the cleaning this has happened.
From the above. Is there anything, that would suddenly cause the battery not to get charged by the bike and/or drain for no apparent reason?
As I said it's been fine until just a few days ago.
Bike is back on trickle charge now. So not sure if my cleaning the started motor contacts up will have done anything.
Any wires/connectors to check?
Any fuses to check?
It's didn't gradually get worse, it's just happened suddenly.