It would be my pleasure to help you any way I can with your Solex.
Yeah, the Cyclomoteur 3800 motor was used on the 3800, 4600, 5000 and Micron, as well as on some other models.
By the frame number, I can tell you that it is a 1972 or '73, most likely '73. If you'd like to know the year for sure, let me know the seven digit number stamped into the top, rear of the motor. It will most likely start with 71, possibly 70.
What color is your 5000? The center motor hood should be the same color as the frame.