Cutting out at lights

[socr8s]

Ever since the London Thunder intermittently when break for traffic lights and roundabouts find that revs drop off dramatically and have to keep foot on throttle to prevent it from stalling. Had heard some people had had problems with V Power and so have switched to using Tescos 99 but does not seem to have made any difference. Any ideas would be most welcome

[Wicker Man]

Time to clean the 'stepper motor' i suspect. It's an easy DIY job that was featured in a Sprint recently.