Hi everyone, I have a 2008 FLHRSE4 Road King CVO anniversary Ltd edition model. It rides beautiful but after about 40 minutes riding the reading on the rev counter drops. E.g. If I'm doing 80mph the revs should read 3000rpm but it has started to show 1000rpm at 80mph & when stopped & ticking over it sows less than zero rpm !!! If the engine is off for 10 minutes or so then it will function ok for another 30-40 minutes. Anyone got any idea what could cause this ?

Thanks in advance
Bob.