New electrical problem: When bike idling with lights on battery goes empty and chances for next start become fifty fifty. Battery usualy mesures 12,8 - 12,9 volts.
Where to look? Voltage regulator? What should be charging current on idle?

If you start the K and just let it idle it doesn't charge. Idling for long period with lights on will eventually drain the battery I think, the charge light often glows on tickover with lights on.
 
If you have a meter 12.8 - 12.9v battery sounds good but when charging should be I think around but not more than 14v

If you put the meter on the battery, then start the engine without revving it you will probably see it drop as the starter turns and then go back to 12.8 or so, then rev it you should see the voltage rise significantly over 13.5v. If when you rev it you see no change then suspect a charging issue. But first check your earths and connections to the battery, if bad they can mean it will not charge.

Ideally you should get 14.2V at 3000 rpm but down to 13.6V is OK but you will find that if you use the bike for short runs the battery will not get fully charged and will deteriorate quickly.
It is possibly just worn brushes but any time that happens you should clean and if possible machine it true and install a new regulator or at the very least new brushes.

nino  have you noticed that the charge light stays on till you rev the bike a little over 1500 revs ?

if you just start the bike and let it idle ..,.the indicator in the instruments stays alight indicating - no charge is occurring ...a quick blip of the throttle usually puts the alternator into full excited mode  as the field current in the alternator reaches a critical level  and the indicator lamp will extinguish .

the battery will still discharge somewhat , with lights on etc running at idle


just a question nino

I thought I read that you placed an oring (rubber thingy ) between the engine and alternator some time ago ?


are you sure that you have a good earth contact to the alternator from the engine ?

perhaps the contact of the 3 mounting bolts to the alternator has become lossy ?

I would be putting a large cable bolted to the alternator body and the earth side of the battery , perhaps at the gearbox - battery earth point

there is a threaded hole (5mm) at the back of the alternator ....I think for mounting a suppression capacitor    that might be suitable

see the attached picture

Thanks Olaf, Rick, Charlie:

Yes the red light stays on after 1500 rpm. I see it at night but not at daylight, but its usual. I put O rings between alternator and engine which checked yesterday and it didnt loose contact. I ll try additional ground wire from alternator to gearbox. Tommorow I ll measure charging. I plan to buy new charging regulator anyhow because this one is old.
Regards

What is the reason behind the O-rings, I didn't catch up with that.

I tried to supress noise from alternator with three O ring between alternator and engine housing. Rick, I have question for you as I red you use 60 A alternator. Is it less noisy than old 32 A alternator?

I have never had a noisy alternator but some I have fixed were noisy because the rubber dampers (monkey nutz) were lose and worn. Once they were replaced all was quiet. If you have any movement in the dampers they will get noisy, the vanes should be a very firm fit.

Nino,  

These are the monkey nutz that Rick refers to.  

I bought new upgraded alternator rubbers from Motorworks and changed bearings in alternator. I am not shure but think that old 32 A alternator housing connected to engine produce a lot of resonating noise.

New voltage regulator mounted, 14.01 charging voltage on 1200 - 1300 rpm with choke on half. Not original regulator, but some germane made item (allegedly), price 20 euro.

good fix nino