Not sure if your just questioning the S or the motor it self so-
what you have is one of these. ( yours is one year newer)
https://www.youtube.com/watch?v=RKTZWCFGwo8
Here is how the ignition works.
https://www.youtube.com/watch?v=zLS6IglCy9k
If the wiring is bad this is one way to repair it.
https://www.youtube.com/watch?v=e2vxDqF_OEU
Only some of the tags got stamped with the S.
Most of the service Speedster’s I’ve seen only
have the serial number.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.