A tachometer - preferably an instrument with a fine scale (0-3000rpm, say) - can be useful for tuning the carburettor. When it is connected to the coil, the slightest twist of the mixture-adjustment screw alters the engine speed. To adjust the mixture, set the screw to give the highest possible rpm consistent with the smooth running of the engine.
The strobe light is usually connected between the sparkplug and the plug cap. Inductive connecti...