22nd February 2014 at 2:50 pm #5508
Hi, I’m having problems with the alternator of my z750B1. My battery won’t charge.
I already changed the stator assy, coil and rotor but I still haven’t got any voltage when I use a voltmeter on the wire end of the coil, so before it goes to the rectifier.
Anyone here who can give me some advice?
M.22nd February 2014 at 4:29 pm #11164
I presume you will have checked for voltage with the bike running. Did you change both coils? Were the parts new or used? Have you checked the resistance of the coils?23rd February 2014 at 12:47 pm #11177
Hi, since I’m not a native speaker and I’m not sure of the correct english words, I’ve put a pic of the parts I replaced. I bought them on the second hand market. Is it possible I have to remagnatize the rotor?23rd February 2014 at 12:48 pm #11178
and yes, i’ve tested the voltage while the engine is running.23rd February 2014 at 12:53 pm #11165
You are not native speaker? Well do not worry your English so far is excellent. You have answered 2 of my questions with the picture and your reply so thank you.
Yes you have replaced both coils.
Would I be right to say you had the same problem before you fitted these ‘New’ parts?23rd February 2014 at 3:04 pm #11170dougytParticipant
Rotor should not need to be re-magnetised as it relies on the smaller centre coil to give the magnetic field required and the rotor will just break down the field to create a voltage. I’d be looking at the regulator.23rd February 2014 at 3:05 pm #11171dougytParticipant
Also is the keyway to your rotor OK, and key in place. The rotor may not be turning with the engine and then it won’t produce a current.23rd February 2014 at 3:34 pm #11179
Hi, Yes I replaced the three parts in the picture. I had the same problem before, so replacing these parts didn’t make a difference. I think I checked the voltage before the current goes to the regulator. I checked the current at the end of the wire of the inner coil so it doens’t reach the regulator yet I think?23rd February 2014 at 8:04 pm #11175MichaelParticipant
the rotor should not be magnetic at all. Alternators with an exiter coil are different than the often used alternators with a magnetic rotor and only one set of coils.
E.g. B3 and later models have this other alternator type.
Don’t get that mixed up 🙂
You may download a manual for the B-models at
It’s a 186 MB file !!!
At around page 175 you will find all the measurements described which have to do with alternator and R/R (rectifier/regulator).
Cheers, Michael23rd February 2014 at 9:21 pm #11166
Some good help and advice there for you Belgiantwin. As you have the same problem as before you replaced the 3 items that tells me your problem is not there. Regulator does sound possible. You need to check the components as described in the manual.
The first test to me is Voltage across battery without the engine running – It must be over 12v
Test the same with the engine running on tick over – the voltage reading should increase
Test the same with the engine running over 3000 revs – the reading should increase again to between 14v and 15v
The readings I have given are approximate but you should detect an increase in voltage at each of the 3 stages.23rd February 2014 at 10:08 pm #11167
By the way Belgiantwin, are you coming to the 2nd International Meeting of the 750 twins at Pont de Deulin in June?24th February 2014 at 8:56 am #11180
Hi, I’ll do my best to make it! Thanks for the invite and info. I’ll try to work on my bike next weekend. What I still don’t get though, is that when I connect my multimeter before the signal goes to the regulator and rectifier (so at the end of the lead of the innercoil) and I have no voltage there. It seems to me that the problem is situated before? Or is it normal that I don’t have any voltage there? I connected my meter to the battery without the engine running, at idle, and 3000rpm, the voltage stays at 12.3. Opening the throttle has no influence.
Maarten24th February 2014 at 10:07 am #11172TangoParticipant
I’m Having the same thing So I thought I may have a problem My Battery also shows no increase on a volt meter while the bike is running?
I take it we should have?
Can anyone test there bike to confirm?24th February 2014 at 12:01 pm #11176MichaelParticipant
with our Twins and their charging capabilities you should see the up and down of battery voltage when motor is
on and idling (approx. 1200 rpm)or
on and at higher revs (approx. 3000 to max. 5000 rpm).
If battery voltage doesn’t show that, the battery will not be charged.
Ok, that is nothing new to you, but that’s the result of that easy measurement accross the battery poles.
Download the workshop manual for the B-models and follow the instructions given there.
Some more complex measurements must be done, hard to describe in a post.
Cheers, Mochael9th March 2014 at 12:17 am #11168
I must ask if you did your tests when the engine was at running temperature. I did not know but apparently this does make a difference.
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