did you get this sorted mate, only I had the same symptoms and a fizzie and the cause was two-fold

Battery not at full charge - 13.85V was the final charge and held for 24 hrs (well down a few mV)

Starter cut off relay faulty

If you have food multimeter you can test both of these

??

Do these 'food' multimeters come banana shaped then? Or in tomato sauce?

FWIW I'd deffo go with dead cells in the battery. Ignition left on for that long would do it. Worth checking the ignition coils haven't burnt out as well.

Tried the rev the arse off it. No different :-( maybe the adjuster is seized as the bike only has 20000 miles on it.

That sounds identical. I have a spare engine that I'm planning to rebuild. Any suggestions on the most competitively priced cam chain sets?

Compression is within values given and all within 10% of each other. Cooling system was fine. But had a small tear in the cap rubber preventing it sealing properly.

Also, at the oil change the, lers call it oil, wasn't a mix of oil and water, to my mind it was oil/petrol mix as oil and water would not mix together but oil and petrol would. The fluid I drained out was left in the workshop for a good week before I disposed of it and it didn't seemed to have separated at all. I'm wondering if there is/was something sticking ie. Float needle in one carb that's allowing the engine to flood massively while switched off,  which it has done twice that I initially attributed to the kids giving it a fistful as they walked past, and this has dumped fuel down the bores and into the sump?

On changing the oil on my 98 there was 6 litres plus in the sump, level was obviously well over the marks on the sightglass, what csme out was a greeny/brown colour and had a whiff of petrol about it. Ive done about 300 miles now since the oil change and I notice the level is slowly creeping up again,  the bike has also been flooding up, with idle, overrun and hot start problems and today, for the first time the fan cut in while riding normally on an A road, no traffic. And stayed on til I shut the engine down about 10 minutes later at this point the it must have overcome the pressure cap as it dumped about 25ml of water out of the overflow.
Anyone have any ideas? I know I need to get the carbs off and cleaned and balanced but is my engine going to be a write off? I'm thinking head gasket or worse atm