We had a 420 in for repair with an intermittent fault that caused it to cut out and although the starter worked, it would refuse to restart for about 20min. The strangest thing was, the dash lit up correctly, except the gear display flashed a line as if it was between gears, despite it being a manual model and the neutral light being on. Of course when we had it in it would run fine. Anyway the owner got fed up with it and traded it in against a Suzuki. Since then it has been stuck at the back of the workshop. A couple of weeks ago another 420 came in, again it would cut out, then re-start after a while, and again the fault wouldn’t come on for us. We sent it back, and it cut out again after two days. This time the fault was still on when it came in. No spark, no sound of pump starting up when you switch on, but dash lit up as if nothing was wrong. Tried a few things, including swapping left with right relays and still no start, but the gear indicator began to flash like the other bike, so same fault. We checked with a Honda dealer’s mechanic, who reckoned the short sub loom for the relays sometimes failed, (it is in the wet muddy bottom of the battery box) so I took the sub loom with relays off it and plugged them into another 420, the fault was transferred to the other bike. Fitted a new relay and the fault disappeared. So, if you get a 2006 to 2014 420 manual that cuts out intermittently, no fault codes and the gear indicator flashing, one of your relays has died.