"The date letters for 1997 are
"The date letters for 1997 are EU so the model number should be E115TSLEU followed by a suffix letter.
Either look at
THIS DIAGRAM or locate your engine in the
PARTS CATALOG and look at the diagram for the ignition system.
The water cooled rectifier regulator (which it seems is fitted to the TSX (25") models) is shown as part #82 in the diagram in my link and the non regulated rectifier (fitted to TSL (20") models) is shown as part #79.
I can't help with testing the regulated type but the non regulated one can be tested as follows.
Disconnect the leads from the nearby terminal strip (remove the rectifier completely if you prefer)
Connect one lead of a multimeter set to the diode test range to the red lead and the other to one of the yellow leads. Note the reading if any.
Reverse the meter leads. If you had a reading above you should now not have a reading or vice versa.
Now repeat the above between the red and the other yellow.
Then repeat the whole procedure between the case and the two yellows.
Each time you should get a reading with the meter connected one way but not if connected the other.
Each test is on one of the four diodes that make up the rectifier.
If you have any blown diodes in there you'll get no reading in either direction on them. If it has been blown by connecting the battery the wrong way you'll find two blown diodes at least.
BTW some motors have a 4 wire rectifier, with 3 yellow leads. Extend the above to the third yellow in that case as they have 6 diodes)
Sometimes it is possible to use one of the ohms ranges of a meter that does not have a diode test range, but not all meters work on all the ohms ranges and some work on none of them. One of the higher resistance ranges is most likely to work if any do I think.
IF JWB is right, and he probably is, then it has the watercooled rectifier/regulator regardless of the shaft length."