TOPIC:

I installed a new battery today and measured approx. 12.69 when everything was off.
Turned the "long" light on and I measured 12.34v

Stated the engine and on idle I got 13, on 5k I got 13.20-13-30.

Is these normal ?

Shall I test more? what should I have ?

I assume the charge voltage is higher if the voltage on the battery is lower (not full) ?

Thank you all.

You assume wrong. I don't think your reg/rec is smart so when you get to 5K rpm, you should see a bit higher voltage at the battery; about 14VDC. I don't know what a "long" light is but a new battery should be about what you measured with the engine not running. The idle voltage is good but you may want to look at a new reg/rec combo mounted somewhere where the air can get to it while you are riding.

The reg/rec voltage measured at your battery is a constant regardless if battery is fully charged or not fully charged or tired.

14.5 VDC at 5000 rpm is what you should be seeing. Low voltage is likely due to a weak stator but it could be resistance in the wiring and maybe even the R/R. Hard to say.

Nessism wrote: 14.5 VDC at 5000 rpm is what you should be seeing. Low voltage is likely due to a weak stator but it could be resistance in the wiring and maybe even the R/R. Hard to say.

I should see 14.5v at 5000 rpm regardless battery is fully charged or not?

I will test more the next days and report back.

A depleted battery will take longer to get up to the 14v range than a fully charged battery, but if your battery is new, and you haven't been cranking it a bunch, it should get to 14+ volts in a few seconds to a minute.

I will do some more tests with charge voltage and stator tests and come back with the results

Today have I done some test of the stator.

Look like my multi meter has a 0.2 ohm offset (attached photo).

1. I checked all three cables coming from the stator against the negative pol on the battery, and all indicated open loop.
2. Measured ohm between the three cables:
A: 0,08 - 0,02 = 0,06ohm
B: 0,08 - 0,02 = 0,06ohm
C: 0,09 - 0,02 = 0,76ohm

3. I started up the engine, and when it was on idle around 1k I measured the voltage from each cable from stator towards negative pol on the battery:
A: 3 - 3.5v
B: 3.7 - 4v
C: 3 - 3.5v

Before I started up the engine the battery had 12.97v on idle 13.15 took the engine up to 5k for some second and the voltage was 13.25,
when I come down to idle it was 13.25v.

What do you say ? Must I replace the stator is the stator the issue ?

Of course, you do realize, the voltage coming out of the 'Stator" (alternator) is AC(Alternating) not DC(Direct), and should be measured, with meter on AC, between each of the three yellos wires which are the three phases, not to ground. It sould be something in the order of 30 VAC between the yellow wires (not sure on the old bikes). This test is strictly for the Stator, not the RR., and of course, the rotor (the magnet) could also be weak, even if the Stator is in good shape.

The RR (Rectifier/Regulator) grabs these three phases alternating current, rectifying them to DC and regulates to about 14.5VDC at running RPMs. This voltage runs the system and goes back to charge the battery. It is really a 14 VDC system. 12VDC is just nominally.

Thank you for all theory, I have now been outside and mesure the AC, when it was on idle the voltage was jumping some... when Itook the RPM up to 3-4k the voltage stable.

A: 5,7 - 5,8 V (AC)
B: 6,0 - 6,1V (AC)
C: 6,0 - 6,1V (AC)

Based on all my numbers here and above in my last post earlier today, what an the problem be?
I assume you other who has old bike and also the same engine, what is normally the problem?

Weak stator based on my numbers ? magnet poor how often is that happens? other thing ?

Thank you for your experience in these matter !

Are you reading without disconnecting the yellow wires to the RR?? When I said about 30VAC, that's alternator spinning, but yellow wires disconnected before you start the bike. The bike electrical system would be run by the battery (I usually connect a battery pack to the battery to help it when doing this test, WATCHING POLARITY). I own a '91 KZ750 (they called it the Zephyr) and this test is from the Kawasaki factory manual. The '91 has a single three-prong connector to the alternator. The 30VAC is also from the manual, but remember, mine is a '91 but still I'd expect yours to be in the high 20's

.2 ohm offset on the meter is normal.

The test described in the manual is like what hugo said:

Disconnect the three yellow stator wires.
Start the bike so it runs off the battery alone.
Measure the AC voltage on each pair of the three yellows (one pair at a time).
Do this at 4000 RPM. Each pair should measure around 50 VAC or slightly higher.

Note:
Some manuals have incorrect information. Some say each pair should have 75 VAC, but that is wrong.
75VAC is for a 1-phase stator (2-yellow wires).

75 VAC is very possible if not expected. I've seen that several times before if not even higher. A high "no load" voltage is not 100% indicative of a good stator though.

When first was working on my 750 i was frustrated to only be getting 13.7 VDC when charging. I disconnected the R/R and checked AC voltage and got about 70 or so. I installed another used stator and it was the same. I figured it was a problem with my R/R so I tried two different units but got the same results. Finally I spent the bucks on a brand new Rick's stator and bang, change voltage went to 14.5 VAC. Problem solved.