Ran out of fuel, now have issues.

[Bandage]

So.. Bit of an update...

Got new spark plugs a new dizzy cap and rotor arm. Gapped them properly. Engine started much better, but still had no power. After about 30 seconds or so the engine would die, sounding like fuel starvation.

Got some of those sparkrite inline teters. All looked good. So spark isn't the problem.

Took the carb off and gave it a proper reset. New jet fitted ( much fun was had trying to fit it into the float bowl!)
Took out the inline fuel filter. Fuel flowing nicely with key at first ignition point, did a pint in under a minute.

Starts, but still no power.
So, spark good. Fuel good. Must be compression.

At this point I called it outside my ability and got it off to a garage.
Head Gasket has blown on cylinders 3 and 4. Not sure the full extent of the problem yet, but hopefully know more later this week

[myoldjalopy]

Oh dear, your first post had a bit of clue - "a bit of a knocking noise and a loss of power".
Hopefully no harm done and a new gasket will sort it