Electrical fault

[motorcyclemangsx]

When I press the horn button, number 6 on GPI on the revcounter is lighting up, any ideas on where to start looking for fault.

[Hooli]

For something random like that I'd be looking at earths.

[gsxbarmy]

When I press the horn button, number 6 on GPI on the revcounter is lighting up, any ideas on where to start looking for fault.

You'd have to go back to @Thommohawk for that as the gear indicator on the rev counter is one of his electrical mods, not a standard feature

As an aside though, I'd check the wire down from your horn button to the horn(s) itself, as it sounds like somewhere it's shorting out. Typical places will be where the wires go into/exit from the headlamp shell and along the side of the headstock.