speed passion gt2.0 pro help

[branstonpickle]

hi hope u can help i used my speedo yesterday and all was fine come to race it today and it goes from haven full throttle range to cutting right down to then bursting in to full range again to then stopping all together leave a few seconds then it is fine for a few laps all wires seem ok motor is ok i have a power cap and have tried setting it up to hand set again but no luck any suggestions.........