Noting that 1243 is 1342 backwards a counter rotating dizzie and/or engine will give that
firing order too. Others fours with a 1243
firing order include many of the Honda bike engines such as the CBR600 F4i engines. Many older cars (Riley) and tractors (John Brown, Case etc) had the 1243
firing order but most modern engines have settled on the more common 1342
firing order. And in my nearly 50 years of playing with cars and engines I've seen that a few times and I have also learnt that you can never assume any particular
firing order and always to check the specs if it's not stamped somewhere obvious like the tuning plate or inlet manifold.