OK... "sigh" I tightened exhaust clamps, reset pilot screw, then kicked and kicked and kicked and nowt but odd backfire. Tried choke full on, half on, off, no throttle, bit of throttle, priming carb but all to no avail. They can't be this difficult to start can they

Is there a "technique" for this or do i need a new set of carbs? I checked the spark by putting a spare plug in the cap & left the bike's plug in situ. Spark looked OK to me...
A bit discouraging if I can't start the thing...