Charging problems

[born to be mild]

Hi All,
My new to me 750 F2 is charging at 12.9v lights off and 12.6v lights on, I took it for a spin today and checked the battery voltage before I left , which was 12.9v, when I got back after about 6 miles of mixed traffic and country lane riding it was 12.6 volts. The last time that I took the bike out was a 40 ish mile run where I ran out of fuel, once Id sorted where reserve was the battery wouldn't turn the bike over, but I got it to fire up on the kickstart. The only other time that I've ridden it is the approx. 100 trip home from the previous owner where it started running rough then seemed to clear which I had thought was carb related, not so sure now.
Before I took the bike out today I swapped its fairly new looking battery for the Motobatt out of my Triumph, so I'm certain that its a charging issue. Do I need to adjust the regulator?, I thought that Id ask wiser heads then mine before I start fannying about with electrics that I barely understand.
Cheers.
Andy.

[martin_uk]

Check all the connections and earths first as common to have a problem with high resistance, especially the rectifier.

This may help you test volt drop http://www.aa1car.com/library/voltage_drop_testing.htm

A poor engine earth may also account for the starter problem.

As a matter of course I always put in extra earths when restoring  to aid reliability

Dont consider adjusting regulator until everthing else has been checked,

[Lobo]

Hi Andy,

Further to Martin's help, this from my K2 manual.... I guess the two charging systems the same.

   RPM                    1000.  2000.  3000.  4000.  5000.  6000.  7000.  8000.
Night riding amps.     6.5.    0.0      2.4.    1.3.     1.0.     1.0.    0.8.    0.6
Day riding Amps.     2 - 3.    1.0      1.0     1.0     1.0      1.0     1.0     1.0
Batt Term Voltage.   12.0.  12.4.   13.2.    14.5.   14.5.   14.5.  14.5.  14.5

Would have so preferred to attach a photo.... bloody iPad playing up... sorry.
Simon

[Bryanj]

Over lots of years charging faults are 75% bad battery; 24.9% bad connections; and 0.1% faulty components

[born to be mild]

Thanks guys,  tested the bike against your figures Simon, and got 12.4 volts at 1250 ish rpm and 12.8 volts at 5000, so I definitely have a problem. Looking at Bryans statistics I will start with the wiring loom and earths as the previous owner had the frame powder coated and also there are some of the scotchlok connectors in the wiring. I'll take your advice Martin and not dicker about with the regulator til I've tried everything else. Thanks everyone for responses so far I will keep you posted in case what I find is useful to anyone else. Thanks especially Simon for going to the trouble with the table and for trying to get photos.
Happy easter
Andy

[martin_uk]

Scotchloks are a problem waiting to happen especially where open to elements, so best remove and use reliable connectors, definately worth the time and trouble to get right.

[Bryanj]

If the frame has been powder coated the coating needs removing wherever the earth leads go and at the main earth strap/ engine mounting plate or all sorts of funny things happen