Hi Harley,
Thanks for your reply. Actually I was surprised too when I found out that it was not a Graupner 300. Electric starter performance is excellent. As I said, the problem seems to lie in the compression spring because when I open the throttle I can see the cone sliding slowly out. I do not believe it is an ECU signal issue because when I throttle down I can see the starter cone sliding in again.
Indeed I know Carlos is a solution but since this is a trivial matter (I hope) it does not make economic sense to send the whole turbine (engine is relatively new - very low run time) half way round the world to change a spring. Might be a wrong assesment on my part but I would like to see what i can do from my end before taking the easier decision. Undoubtedly, if I felt that the problem was more serious I would not hesitate to send it like I did when I had an ECU issue.

Anyway, thanks again for your feedback. It is appreciated.

Reuben