RPM pick up

[Spider001]

Has anyone had problems with the RPM pick up on a dyno? Ive had mine on the dyno today, but the RPM trace drops out at about 4000 rpm. Ive tried it from the black wire on the ECU and the wire on the coil stick but it still seems to do the same thing? It's fine on 80% throttle, but when run to 100% throttle the RPM trace drops out at about 4000 rpm and comes back in at about 7000 rpm. It seems to be when run at 100% throttle load? Can anyone shed any light on this? Is it a common problem with BMW R1200S? Anyone got a solution for this? Many thanks for any help.

[nige1200s]

Not had mine on a dyno but is this something to do with not firing both plugs all the time. This could make sense if you are connecting to the lower plug but the centre plug should fire all the time.