Dry spark may be cause by a low level in float chamber or no fuel in float chamber, check it with a transparent tube
Dry spark may be cause by a compression problem, check it with a compression tester, if you don't have : remove carburators, displug ignition coils, press start engine and put your other hand on the inlet pipe number 2, you should feel an huge succion, compare with all other cylinders.
En tout cas, c'est compréhensible pour un anglophone 