If that smoke is black, the mixture is too rich to fire or there isn't enough compression or the spark timing is wrong. You've probably carboned-up your new plug a bit too, but hopefully it will recover when you get it running.
To get it to run you need 4 things: a suitable mixture of air and fuel in the intake manifold beyond the carburetor; compression in the crankcase when the piston descends; compression in the cylinder when the piston ascends; and a strong spark at the right time. If you haven't done so you should check that all four things are happening, each in its due season. Starting with the induction process, is there a pulsating suction at the open end of the carburetor when you spin the engine with the spark plug installed (but disconnected, for safety)? If yes, can you feel crankcase compression on the down-stroke and cylinder compression on the upstroke, so you feel two resistance pulses per revolution? If no crankcase compression, you may have severe piston scoring, or leaky main bearing seals. If no cylinder compression, you may have a problem with rings, or with a decompressor if you have one. If you pass those tests the base engine is probably OK and you just have to worry about air/fuel ratio, spark, and spark timing.
Bruce has told you the usual way to test for air/fuel mixture problems. It bypasses things like intake manifold and bearing seal air leaks - if you have cylinder compression and correctly-timed spark, it should start and run for several seconds. If it doesn't, and you have good blue spark, there has to be some suspicion that there isn't enough compression - it is hard for a Victa's ignition timing to change.
