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the photo you have is a single phase alt rotor. nothing like a 3 phase. all st4 are 3 phase - 1999 was the first year of 4v 3 phase alts.

this is a 3 phase alt rotor. not sure of aftermarket options, it's a pretty unique and never fails, so low demand part. lots of s/h ones on ebay or someone like mike at gotham should have a shitload of them.

Wheel Automotive tire Rim Automotive wheel system Circle


the stator looks like this and bolts into the alt cover. lots of aftermarket options - electrexworld, ricks, etc. it's a part that fails.

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Curious :unsure: almost looks like there is only 2 wires coming out of that 3 phase alternator, a 3 phase alternator by rights should have 3 wires for output.
i didn't look at the number of wires, so you are correct - that photo is of a single phase stator.

but you'll note that i said "looks like". i just found a stock photo on an ebay listing to illustrate to the op what he needs to be seeing, because he really has no idea here.

if you remove the alternator cover on a belt drive ducati engine and turn it over, you will see one of two possible alternator stators types. if it looks like the photo above, it's 3 phase. if it looks like the photo below, it's single phase.

single phase alt stator
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Update: The fog is starting to clear.

The net is that I don't think that I am missing this part, and that the workshop manual is in error.

1. I received the Jodi from Euromotoelectrics.com the 'round thing with magnets and a keyway'. The hole is too small for the threaded part of the crankshaft... Regardless, Jodi's service and response was exemplary.

2. Without this part, i.e. with just the flywheel, there are sufficient threads to properly torque the castle nut which supports Brad's point that this is not needed.

3. Ducati Parts USA replied with part # 27610281A for the flywheel, which also supports Brad's point.

4. Below is a screen shot from the Service Manual. #4 is what caught my attention. It seems that the manual is in error.

View attachment 107079


5. Indirectly related, I looked, and was surprised to see 3 AC wires from my 1997 ST4. From researching an ST4s engine swap into and ST4 I expected to see only 2 wires, 1 phase. Happy days, and my 110k mile ST4 continues to run fantastically.

While it will be some time before I'll be able to get the ST2 started to verify charging, I think that I'm good (although I'll probably replace the regulator as a matter of course.

Guys, huge thanks for your thoughtful responses! I will update if I learn anything further. The more that I learn, the more that I find that I don't know.
it's not fog, it's the wrong manual. the manual you show is 97-98. it's not in error, it's showing exactly what a 97-98 looks like. the water cooled engines went to 3 phase alt in 1999. get the right manual.

you can't have a 1997 st4. st4 production began in sept 1998 for 1999 model year bikes. yes, it will have 3 wires as it has a 3 phase alt.
 
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