How do I fix drive problem on Frister Rossmann 110?

I cannot get a proper "drive" between the motor (which is working fine) and the shaft and the belt is adequately tight. I have taken the plastic flywheel off but cannot see any way how the power is tranfered. Shaft will turn ok by manually turning the inner knurled wheel and everything looks to be greased and lubricated that should be. Sorry about the terminology, but I am more used to working on cars than sewing machines. Many thanks for any help/suggestions in advance.