Alfano rev counter issue

I have an alfano pro from my sons karting days.
It has 2/4 stroke function for rev counter which involves pickin up a pulse from the HT lead.
Anyone know why it does not work on my scooter ?
I am running a Varitronic with standard CDI if that helps.
It has 2/4 stroke function for rev counter which involves pickin up a pulse from the HT lead.
Anyone know why it does not work on my scooter ?
I am running a Varitronic with standard CDI if that helps.