All 38 degrees downdraught Scott carbs dribble petrol after the tickler button has been operated because that puts the petrol level above the primary airway. It stops as soon as the engine is running, and is nothing to worry about. Screw the primary air screw fully in (gently !), and then unscrew it 1.5 turns for an initial start up. Fine adjustments can be carried out later.
Have you tried switching the plug leads over ?
Also check that you have crankcase compression. Remove the spark plugs, open the throttle fully, no choke, and with ignition OFF, and petrol OFF, turn the back wheel forwards with the bike in top gear. You should hear a ‘plop’ noise twice per engine revolution, like a cork being pulled from a bottle. If you do not hear this noise it is likely that the cylinder base rings are defective or missing. If you have to renew them only use the latest ethanol resistant ones. Ian Pearce sells them but I don’t know the spec of the Spares Scheme ones. Perhaps someone can comment on that ?