Ok, thank you very much. I only need to tighten the screws in the centrifugal clutch to make it spin with the shaft, but I can't remove the first gear on the same shaft -- it's attached by bearing to the 2nd gear or something like that.

I will try to get an Emaxx input shaft, that does sound like the best option for slipper.

I ended up buying the 1527/1y (1250 kv.) neu motor btw.