It was easier for the manufactures to balance the engine, to prevent vibrations, if the firing order was 1342.
1342
1342
1342
1342 on 4 cylinder engine
1342
1342
the firing order is as follows : 153624 if its a 4 cylinder it is 1342
1342 in an anti clock direction.
1342
1342
1342 if it's the 1275 cc engine, with no. 1 at the front of the engine.