Wingman1946 asked that I try to clarify and simplify the "Three Nylon Screw Mod", so we'll give it a go.
I've not done this mod, and have no plans to do so, but understand the procedure.
This mod was cooked up long ago by other members, and is intended for one specific application scenario:
Modifying a B-type 70-79 alternator to allow the use of later A-type 80-on combined solid-state regulator/rectifier.
Other combined rec/regs may be used, if they are the A-type, which provide a regulated
grounding for a
powered exciter/rotor.
Reference threads for this mod:
http://www.xs650.com/forum/showthread.php?t=4170
http://www.xs650.com/forum/showthread.php?t=6477
http://www.xs650.com/forum/showthread.php?t=11947
http://www.xs650.com/forum/showthread.php?t=18358
http://www.xs650.com/forum/showthread.php?t=38428
http://www.xs650.com/forum/showthread.php?t=41778
http://www.xs650.com/forum/showpost.php?p=418291&postcount=10
The B-type 70-79 alternators rotor brush configuration:
Regulated
power (green wire) is supplied to the outside brush.
The inside brush is
grounded through the case screws.
The A-type 80-up alternators rotor brush configuration:
Regulated
ground (green wire) is supplied to the outside brush.
The inside brush is
powered by switched power (brown wire).
To achieve this, the alternators have these differences:
The alternator cases have different brush block mounts.
The brush blocks have a different screw hole above the inner brush.
The inner brushes have different hold-down brackets.
The wiring lugs to the inner brush go to different screws.
An outside view of the two different brush block configurations:
View attachment 54790
An inside view of the two different brush block configurations:
View attachment 54791
Two styles of regulators exist, and must be properly matched to the respective alternator.
- "B" type regulator that supplies
power to a
grounded rotor must be used with a 70-79 alternator configuration.
- "A" type regulator that
grounds a
powered rotor must be used with a 80-up alternator configuration.
This mod allows the use of the later style A-type
grounding regulators on a 70-79 alternator.
First, replace the three M4x0.7-12mm steel screws that ground the inner brush with:
Three M4x0.7-12mm Nylon screws that will float/isolate/unground the inner brush.
Next, the black wire that originally went to ground on the inside brush must be supplied switched power by splicing it to a switched power (brown wire).
The original first method is to cut the black wire on the main harness side of the alternator connector, leaving about a 2 inch pigtail, to which a brown extension wire may be soldered and then spliced into the brown wire (switched power) of the new rec/reg.
Another second method that may be easier, is to cut and splice the black wire near where it connects to the regulator connector.
This is my old 1971 XS1B main harness, uncovered to reveal that the black wire simply connects the regulator and alternator brush. There is NO additional connection to this wire. It is independant, and NOT grounded. Grounding for this wire is provided by the inner brush's mounting screws.
As such, once the black wire is cut, the rest of the wire that goes to the old regulator connector is NOT grounded. That end of the black wire must be grounded, or spliced to another grounded black wire, if you expect to get ground at that connector.
A close up of the black wire and the two possible locations for cutting and splicing.
This regulator connector location (on a 71 XS1B, thanx Angus!) is much easier to access, and conveniently near a brown wire.
However, this second method needs to be confirmed, as the black wire may attach to a grounding point within later 72-on main harnesses. A simple test would be to disconnect the black wire at the inner brush, unplug the regulator, then test for continuity of the black wire to ground...