750SF1 - after some months of non-use. Went to start it and nothing... Battery? or Starter Relay?

[aircooled1]

1972 750SF1 - after some months of non-use I ambled into the cold garage and wanted to here the Laverda start up. Went to start it and nothing happened when I did the usual ignition procedure of key in and down - turn to right and fire the Starter Button. Result: No sound at all of the starter.
I could see the headlight works ok with key on.
I then tested voltage on the battery and I am a bit suspicious as it says only 10 volts. My battery tender says its full which I think is a fib. I tried to by pass the starter relay and the starter would not make a sound at all. So is that test confirming a weak battery? That it simply cannot budge the starter?
I also tested the handlebar switch and it does send voltage to the starter relay. I also tested the starter relay and found that it did not seem to pass on the voltage to to the starter. It does have battery voltage to the incoming side of the relay. So I feel my diagnostics are scattered. It seems the starter relay is not functioning properly AND the starter won't work when directly powered from the battery. It can't be both things gone wrong. It started fine a few months ago.
Suggestions? Should I just get a new battery ? Or disconnect the starter relay and test it better in isolation?
I will say that the horns do not work currently as I suspect the horn relay. But I am doubting this could be the cause because I bypassed it all when I hooked the battery directly to the starter and it did nothing.

 

[arancia]

I then tested voltage on the battery and I am a bit suspicious as it says only 10 volts.

A no-load battery showing 10V suggests it's dead!
Try charging it for a couple of days or jumping starting with another known to be well charged e.g. car battery after you check all the basics like has fuel, oil level, etc.

 

[Andy]

As above.
The charger is trying to push power in but the battery is not taking it, so the charger thinks it’s full.
Assuming that your volt meter is correct
Also when testing the relay, remember that the high current side is just a switch, so test both sides to earth. But the low battery voltage is likely the problem there too. If you test the battery voltage as you press the button, does the voltage dive way lower? That’s another proof, if you needed more

 

[Paul Marx]

Put a set of jump leads direct to starter and see what happens. If the starter turns, put the jump leads on the battery terminals of the bike.

Paul

 

[3C-Wayne]

Battery has 6 cells each producing 2 volts, one of your cells has shorted.

 

[Laverda1000.de]

I will say that the horns do not work currently as I suspect the horn relay.

The original horns will not even make a feeble peep if the voltage is to low, relay or not. More modern ones might still make some kind of sound with lower voltages.

 

[henrywillms]

I had a battery tender that was working good then it went into state where it said battery was charged but it wasn't. Like you bike would not start and voltage test showed low battery. Charged with good charger and all was well.

 

[Paul Marx]

What happened with the jump leads then?

 

[helicopterjim]

I had a battery tender that was working good then it went into state where it said battery was charged but it wasn't. Like you bike would not start and voltage test showed low battery. Charged with good charger and all was well.

I had the same ...... my Optimate 4 would charge up the battery and indicate that it was good ...... but then it would pause for 30 minutes and then it would indicate the battery was junk. I put my meter on after a charge and I could see it slowly dropping from 13.5 to 9.8 in about five minutes.

Jim