I did small research for that but I couldn't find similar problem. sorry if answer exist somewhere here.

I tried spin very simple assembly from two parts in motion analysis with gravity and gear mate, but didn't worked.

When I tried without gravity but with rotary motor and gear mate works.

I can't understand why that happen. Obviously i did something wrong.

Does anybody know how to sort this out?

Sorry for my English.

Thank you for your help.