The replacement Leroy Somer motor, LSMBT82, supplied by Amel to SM owners is slightly smaller in diameter than the original.
I had to space out the black ring to get it to fit.
HOWEVER, after a visit to Amel in La Rochelle last week, I discovered there is a black spacer for the motor cover that fits this new smaller motor.
The part no. is 01994 - Collerette Capot Moteur LSMBT82 Eu40,06