There are no detailed circuit diagrams available for the M3W. Try a Google search for "checking a motorcycle generator" and you will get the required information. There is a 4 pin plug from the Rectifier that will give you a test point for the generator windings. Hope the problem isn't there as that is an engine out task to replace.
If the rectifier/regulator is the problem the original CE item can be replaced with a Harley one, numbers are in the Alternative Parts List in the "Owners Resource" at the top of this forum. Check the 4 pin plug closely as this has caused problems with poor contacts before. Details for this are also in the Alternative Parts List.
