How do I test for a bad regulator or stator on a 2004 gsx-r?

Question

What causes these things to go bad?

Answer 1

check voltage across battery terminals @ 5k RPM... should be around 14.2v, much less bad stator, much more bad reg/rec

You have to have a good battery to test this though.

Answer 2

Top Contributor gave you the procedure to check if the charging system is working.
And yes you do need a good battery for this test to be accurate.

Unplug the stator connector (the stator is in the left crankcase cover).
Set your multi-meter to 100 AC volts.
I'm not sure what color wires Suzuki uses, they used to be yellow and probably still are.
3 of the stator wires should be the same color.
Label each wire as A,B & C
Test the voltage output of each winding (pair of wires).
Put you meter's leads on A&B then B&C then A&C
Start and run the bike.
Rev the engine and the reading of each pair of wires should go well above 50AC volts.
If yes - the stator is good - the problem could be regulator/rectifier, bad wires/connections, or dead battery won't take a charge.
If no - there are a few more tests to check if the stator needs to be replaced.

Answer 3

Guardrailjim has given you a good answer.
I remember the wires as yellow also, I don't think they changed. I also remember in excess of 100 volts AC.

I also recommend a manual. Clymer's are good ones. (what I use for my Jap stuff). Best $15 - 40 you'll ever spend.

See your other questions.

Answer 4

Before you go further with your bike, you should obtain a service manual for it.

Service manuals cost around $30 to $40 new and usually less than half that used. Ebay, http://www.alibris.com and http://www.biblio.com are good places to find used manuals.

Answer 5

buy the repair book or visit dealer they can give you ohm meter specs for this test

Answer 6

Do not check it at 5000 rpms. Idling is just fine. your looking for 13.2 to 14.7 volts.