Katana Owners Club U.K.

If either reg/rec or alternator has gone you'll need to replace both as they tend to fry each other

Approx 70 volts a/c from each phase on alternator above about 4000 rpm

Between 14.5- 16 v dc across battery same test conditions

Good luck

First thing is check all 3 phases are putting out above volts

As for rewiring I never did it on my old gs 750 just replaced alternator wit electric one and fitted Honda super dream reg rec with extra feed wire cut off. Never had any probs after that

right first thing. you need a VOLT meter, not an ohmmeter. and you need it to be set to DC voltage, thats a symbol of a straight line over a dotted line, (a wavey line over a dotted line indicated AC.
first put them on the battery, red lead to + and black lead to -. expect between 12 and 13.5 volts.
next repeat this test with the engine running, but ticking over, you shoud get between 13.5 and 14.5 volts (ish)
next rev the engine over 3000 rpm with the lights on, and do the same test, you should get the same 13.5 to 14.5 volts. if you are getting over 15 volts or if the voltage keeps rising with revs, your reg rec is cooked. if your voltage isnt rising above what it started at, or even drops as you rev it, then it could be reg rec or alternator.
stop the engine and turn it off.
disconnect the reg rec, find the 3 wires that come from the alternator. in any order at all, test them against each other with the tester on its continuity test setting(the beeper or buzzer when you touch the probes together.) testing any pair you should get continuity, so if you number the leads 1,2, and 3, test 1+2, then 3+3, then 1+3, and you should get continuity, the beeper sounding, for all three, next hold one of the leads from your tester to earth(the frame or the engine casing) and test all 2 alternator leads to earth, any beeps from the tester mean the alternator is goosed, (same as any lack of continuity between the pairs of leads) if they all test out ok, your alternator is ok, and your reg rec needs looking at, though its worth making a lead to earth the body of the reg rec back to the - battery terminal just in case.
alternators and reg recs can be bought new from electrex, better than the suzuki parts, british made and guaranteed, and almost as cheap as a used part from a breaker.

First thing to check is number of wires . 3x yellow 1x red 1x green 1x black is a Honda superdream one , which is a good and common fix.

The Suzuki one has 3x alternator wires could be yellow OR if genuine yellow/white, green/white and red/white. 1X red 1x black white.( tese 2 are the same aftermarket or genuine)
If gen Suzuki make sure black white is connected to the 10mm that bolts the battery box to frame AND thae the small extention then goes to battery. ( better still add length direct ) .
If Honda one connect red and black together and connector to red of the loom for reg reg feed . With out this the loom doesn't know the ignition is on . ( it's a *onda thing.) THE GREEN IS EARTH.