Hand throttle & cross shaft.

[Ian Williams]

Sounds like the brass lever at the bottom of the control tube has slipped, when this happens the lever on the cross shaft is not moved up far enough to engage with the dog on the accelerator pedal. Set the control arm in the steering wheel to shut, loosen the clamping bolt on the brass lever at the borrow of the control tube and lift it until the cross shaft arm almost engages with the accelerator, tighten clamp bolt and all should be well again.