Using a Power supply to drive starter is unlikely to work. I've tried a 10A unit on my starter after reading this, and it was a bit slow. I generally use a 7A Gell Cell (Motorbike battery) to drive my starter and sometimes on a 120 it struggles a bit, so I drag out my electric flight charge battery (about100A) and it spins easily. I have a number of 4ST from OS26 to YS140 and find that it is difficult to start any of them by flicking, but most start with one touch of a starter, after turning over for a few secs on full throttle WITHOUT connecting Glo Plug.Then back to low throttle connect plug turn with starter and bang they go.