Defective battery or charging problem or other?

[billdn]

Having been locked down and then trapping a sciatic nerve for weeks have been unable to ride and battery appeared to have died. So battery recharged but all is not well. Battery after charge read 12.35v, installed and run okay but horn wouldn't work when running but when engine off but ignition on would, for starters. So tried charging volt test as per Haynes manual(all I have) Results dont seem right
1200rpm (tickover) =12.34v
2000rpm  = 12.2v
3000rpm  =12.2v
4000rpm  = 12.22
 Lights on
1200rpm  = 12.13v
2000rpm  =12.6v
3000rpm  = 15.5v
4000rpm  = 12.3-15.5v (erratic)
With engine running and lights on voltage at same revs as above was consistent between 12.3 - 13.6v but when pressing horn just a faint short beep

I've checked continuity on horn -ok and cleaned up earth where bolted to coil on l/h/s of frame.
The rectifier has continuity too and the voltage regulator - gaps and connections appear in order.
The voltage regulator check mentioned in Haynes , is confusing me (attached) I believe I, need 2 meters -ammeter and volt meter ,as I only have a multimeter , am I reading it correctly?
Battery is a multi batt and my be 3-4 years old . Any ideas where to go next! Or is it just the battery!

[billdn]

Oops forgot the P.S. when lights are on the voltage fluctuates and the lights dim briefly then the voltage drops then returns to higher level but does it several times. Just to add more confusion to the mix!

[Bryanj]

Sounds like its charging but battery not accepting it. Modern batteries do not like going flat. Try charging it over a few days and see if it improves also use kickstart for testing not electric

[taysidedragon]

A multi meter is a voltmeter and an ammeter, just switch scales.

[billdn]

Cheers both, but Gareth the article reads like I need to connect one to read amps and then switch connections to do volts but at different positions , or am I just brain addled with electrics after todays session!

[mike the bike]

Unless you're using a clamp meter, a multimeter can only measure current when connected in series with the battery. In other words, remove the positive lead from the battery and connect the meter leads in between.  For this reason, most people stick to measuring voltage.

[Bryanj]

BIG THING multimeters DO NOT measure high current so if you put one in the press the starter button its goodbyeee meter

[K2-K6]

I'd initially suspect the battery may not be quite right as indicated by Bryan.

12.3v after charging is on the low side, suggesting it's impaired.  Reasonably accurate check is to charge it fully with it removed from bike,  then record volts after about 15 minutes,  then just check battery voltage and record each hour over the day.  Healthy,  it should stay about 12.6v to 12.9v over a 24 hr period.  Heading south from 12.4v usually indicates they've not much practical life left in them. 
What can you do with this?  Probably only one of the adapting chargers that can pulse charge it up toward 17 volts to try to revive it's status. This attempts to de-sulphate the plates to improve performance,  but if you've not got one of the chargers it would be better money spent on a new battery to be honest,  especially if it won't hold above 12.3v sitting on it's own disconnected.

https://www.tayna.co.uk/quad-bike-atv-batteries/varta/ytx14-bs/?gclid=EAIaIQobChMI_KzhoYyn6gIVia3tCh24wwAcEAQYAiABEgIo3fD_BwE it may be this size?  But these battery and this supplier are very good.

Because your voltage stays steady when running with lights switched on,  that suggests the load in that circuit is taking the place of the battery and allowing a smoothed response from your regulator. 
One way to check easily,  if you've a car,  is to remove bike battery and connect bike to car battery with jump leads.  Then start and see if voltage is stable from your regulator (effectively using a known good battery to eliminate the bike one)
To do this, connect positive to your bike's red battery feed, then wrap it in something to insulate it from touching anything else, then connect the earth straight to anything substantial on the bike's engne/ frame. Afterwards,  remove earth first.

[billdn]

Thought I'd take the plunge and buy new battery, the old one must be over 4 years old , and if was throwing a curved ball into the equation , technically by replacing it with a known new one should prevent any tail chasing - alas would appear was not battery. Did same voltage test as before and had similar results although voltage did jump up to that specified now and again and the horn worked.....then it didn't and the voltage input remained around 12.3-12.5v! So began testing rectifier with multimeter and cable broke off probe and which point when to pub, oh couldn't but opened a can instead.!!!

[mike the bike]

Check the resistance of the yellow wires from the alternator.  Yellow to yellow,  yellow to other yellow,  other yellow to the other yellow.
They should all read roughly the same.
Also check each yellow to earth , should test infinite.
If you've got one or two phases missing, it would account for bad changing.

[Menno]

Start bike,
let it idle.
Pull the minus cable from the battery while the bike is running.

If the bike stalls, it is either your rectifier or your alternator.
If the bike keeps running it is your battery.

[Bryanj]

Check cleanliness and tightness of all connectors especially engine to electric plate block.

I have had one regulator where the moving points would occasionaly "stick" in the middle open position and that was on my 500 in 70's

[ka-ja]

Check the regulator points and clean up faces with some fine wet and dry.

[billdn]

Not ignoring your advice guys, just waiting for replacement multi meter to arrive.!

[billdn]

So new multi meter in hand of to the workshop! And the scores on the doors read thus:-
Rectifier - appears ok and is giving same values as a new one I'm using another project 400/4 -check!
Field coil - should be giving between 4.6- 5.0 ohms and is 4.9 ohms and is also showing no continuity between white and green wires as required - check!
Stator coil - should read 0.61-0.69 ohms on yellow wires (according to one manual either Clymer or Haynes, forget which) and is giving between 0.13-0.15 although all yellow wires give same reading more or less when tested between them. From connector block which has 3 yellow wires, 1 white, 1 green,1 red/blue and 1 red/green wire only the red/blue and red/green wires are showing continuity - the question is have I found the fault and would this stop the horn working?
only problem now is trying to remove alternator cover screws - 3 out and 1 will not shift , mindful of not breaking lug off of cover too! Sprayed with penetrating oil and wait and see.
As a footnote bought a simple clamp type ammeter and when starting bike dial registers big surge to start then returns to zero.
Any ideas, anyone?