Not charging

Bike is a 1980 Z250 G1,
Battery is ok, Stator is ok, R/R is ok
(i've tried a combo of these as I had spares from a working donor bike as well as multimeter tests)
Bike running without the headlight on the battery sits at 12.4volts. (it drops with ingition and then picks up again to 12.4) It holds it's charge ridining around without the lights on (rode it for 30mins with no drop in charge)
Bike running with the headlights on, it drops to 11.5 and then keeps dropping.
tail/break light issue - This remains On full and if I hit breaks it will not register.
If i disconect either one the of the two sets of wires to the break switch at the pedal it
lights up correctly when break is applied.
... the bike has been left out in the rain for the last 2+ weeks uncovered.
Does this sound like I have a short somewhere?

Would charge the battery -- assure fluid levels within specs and charge overnight at 1.5 amps -- and then have it load-tested.

Voltage measured between battery terminals at idle should be 13+ volts.

Assure battery terminal connections are clean and snug.

Verify integrity of ground connection where the negative battery cable attaches to the engine.

Good Fortune!

Could be as simple as a bad battery, charge it at a slow rate overnight and check the voltage of the battery after it rests for an hour or so. The voltage will be 12.5 to 12.7 if it is good. If it is below 12.4 it is more than likely bad. You can take it to be checked, over here most Auto Parts stores would do that for free, no Idea about the UK.
You say the Stator is good? Have you checked the AC voltage coming out of the Stators wires when running @4K RPM, regulator/ rectifier disconnected? If 2 yellow, single phase, you should have 75 ACV. If 3 yellow, three phase, then test each combination of the three and each should be 56 ACV.
You need Stator output for the R/R to convert it to DCV. How many wires and what color are your R/R?

I've tried it with two battiers , One was at hitting 14.5 in my other bike when running.
So i think that was is ok for sure. I've cleaned bettery terminals, replaced negative lead.
I'll charge it again though just to make sure.
I did find today that as soon as I put the key on the on position the battery started draining.
When I started and road the bike it mainted 12.4/6 for rinding around in cicrles for 40mins.
I'll run the other tests once it stops raning again..

RR has 5 wires, Single wires red/white,brown . 3 pin Yelow x2, black,

No rev counter on the bike so can't go off the revs.
It's the two yellow wires coming from It was purducing around the
same output on both I hit 60 at what was a "decent amount" of revs.
Battery is staying below 12.4 I couldn't get it tested.
So i've ordered a new one which arrives tomorrow so I will run tests again.
It still sits on a consistant voltage and seems to charge ever so slightly when the lights are off but as soon as the lights are switched on it starts draining.
The more I've read it could be the altanator rotor ? hope fully just the battery...
More tests on saturday I guess.

So looking at the manual again It say it should be "about 60V" at 4000 revs
So that is looking ok.
Hopefully new battery is the wining solution

New battery same story,
Getting same readings, tired combo of 3 stators and 3 R/R.
Battery still drains at a very fast rate as soon as the key is
on and faster when the lights are on. It "charges" enough with the lights
off though but not at the expected 14+ volts.
I disconected the tail/break light and readings were the same.
I've realised that the the indicators lights (netural,highbeam,turn)
are not working now either. The illumination of the speedo etc work
when headlights are on.
Next step replacing the flywheel? or could it be a short somewhere still
causing it to drain and not charge?

scraps wrote: ...Battery still drains at a very fast rate as soon as the key is
on and faster when the lights are on. It "charges" enough with the lights
off though but not at the expected 14+ volts...could it be a short somewhere still
causing it to drain and not charge?

Possibly corrosion in the ignition switch and/or the kill switch. Just guessing.

Good Fortune!

looks like I found the problem, Hard to see the pics but the magnet on the upper left has two dents in it. One of them is pretty deep but other wise magnets look ok. the Orange sludge in there I think obviously insn't good either cause by the drop n magnatisim?

Now I thnk I've caused another problem but accidently turning the fly wheel,
I turned it to the left a fraction trying to get a better look at the dent.
I turned it all the way around to what look to be the origional location.
It moved indepently of the chain will this cause a problem wth the timing ?

Now the decision to swap over the head or swap the flywheel.
the rotor on my old engine appears to be slghtly differnt so I may have to swap the top end.

Looks like it's had impact for sure, the dents are pretty deep
no idea how this could have happened.
the stator cased looked in good condition.

The flywheels are the same size, but the marking locations are off.
the yellow one is from my old engine.
yellow spacing between F and T s 18mm , Damaged one is 10mm
The spacing between the other lines 28mm the other 10mm.
Magnets are spaced differntly to the scews on each,
the yellow one has two raised pieces as well.
Would this effect the timing if I used either combo