My observation could be controversial, but I just talk about stuff I've tried that works. Shit cliffa beat me to it more or less. Although I'd still use the ignition switch to turn on power to the TriSpark.
TriSpark is really fond of a dedicated ground from the battery. Just hooking up the Red wire is not as good as adding a dedicated ground wire all the way from the battery to the pillar post your TriSpark Red wire is connected to. Go over your timing routine again. Piece of cake to get static timing very close with TriSpark.
Carburetor troubleshooting is best delt with by taking the carburetor apart and checking everything. You might have an air leak at the intake manifold connection to the head, or a cracked carburetor boot. Slide could be worn or have the wrong cutaway. Could even be a head gasket leak. Loose exhaust header can cause some fun stuff to happen as well.
Sooty plugs can be timing, carburetion, or both. Gotta check it all. Put some new plugs in it while you are at it.
Who rebuilt the motor?
