Ohh I see the confusion... Nc30 only has one hose from the tap, so is gravity fed, no vacuum

The nc 30 should have two hoses at the fuel tap.

I should either drink more or may be less, for reasons I cannot explain, thought your bike was an NC35.

Yes NC30 has vacuum tap, you should have two hoses and fuel should not flow when engine is not running no matter which position the tap is in. If fuel flows freely from tap with tank off the bike, then tap is either faulty or modified and if modified does not need the vacuum hose from the intake.

So here's the update... Bike is fixed!

My fuel tap has only ever had one hose for the time I've had it, from tap to carbs... When tank is off the bike fuel will flow freely when tap is on/reserve but doesn't when turned off...
So the problem...(which I'm now putting down to the fuel tap obviously being left on, not needing a vacuum and somehow passing through)...
A lot(4 litres or more?!) of fuel had managed to find its way into the oil sump, there for causing it to run like shit and die as previously explained...
Drained it out, fresh oil, ran perfectly once it had bellowed out enough black smoke to seriously worry the neighbours, changed oil again and now it's running perfectly...
Guess I've got a tap issue?... Tank will be staying off the bike if im not using it for a while from now on...

Hrc mod has been made to it sounds like - do a google search. I think a fuel tap repair kit replaces the bits you are missing (but check that first). Those more knowledgeable than me will be able to comment on you running the bike with 4l fuel in the sump, as I would have thought it's not great for the engine!


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"HRC" taps work ok on road bikes, just need to be turned off when not in use for extended period. If the carby needles and seats are working ok, even if the tap remain on, fuel should not flow through to the sump.