Dead Battery?

Went to start up my bike after the winter, and when turning the ignition to "on", nothing happens. No lights, nothing. Poking around with a multimeter, continuity seems correct everywhere I check (which would make sense since I didn't play with the wiring really), but the battery only measures ~6.4V. When charging the battery over the winter, the charge level needle on the charger swung up to the top, but the "fully charged" LED never lit. Is that voltage low enough to keep even the idiot lights off? Thanks as always for any wisdom you can provide!

Buy a new battery.

Also, when charging a motorcycle battery you must keep the amperage of the charger set at or BELOW 2 amps. Otherwise you will shorten the life of the battery. Also, do NOT try to start the bike while it is jumped to a running vehicle or charger as this can damaged the bike's electrics. Ed

Yup, I know those bits. Sounds like it's time to do some battery shopping, sigh. Thanks!

For those keeping score, got a new battery and she lit up like Christmas. Didn't think a battery would go from starting the bike fine in the fall to not even lighting an idiot light in the spring, but there you go.

I had a battery in my lawn mower that was starting its 4th year go bad a few weeks ago almost instantly. I kept in on charge off and on all winter ( and previous winters ) and it started right up and I mowed the grass a couple times already this year. Then I the next time I went to start it it was nearly dead. I threw a charger on it and it appeared to take a full charge but it would barely light up the dash lights and it wouldn't even turn the engine at all. I feared there was something more wrong with the mower engine. I jumped it with my truck and it turned over and started after charging for a few minutes. But after disconnecting the truck battery the mower only ran for a minute or so and then spit, sputtered and died. I replaced the battery and all was well again. In fact it was only after I changed the battery that I realized how the previous one was underperforming. The new battery turns the engine over a lot better than the old one and it starts right away. With the old one I had to crank it over a few times before it would start. So anyway, way too long of a story to simply say yes, they can go from being adequate to completely junk very quickly.

Yea, I've had batteries that were turning the engine over good as new, and suddenly fail mid crank. Buying a new battery is no guarantee either. I had a 1993 E350 van, bought a new Motorcraft battery and it worked great, 2 days later, no lights, no nothing, battery dead.

Similar thing happened to me with my old truck. Battery was working fine; no problems at all. I stopped for a burger, and when I tried to start the truck - nothing. Something internal must have broken because the voltage went to zero. Ed

On service free batteries you can´t check the acid level or refill distillate water. If one cell is dry or under the recommended
level the electric voltage get a drop ( internal resistance of the cell by plate sulfation by over charging and / or battery not in use) . The recommended voltage and current dropped immediately when you try to start the engine.
Some electric charger can do a de-sulfation cycle to refit a battery but if one or more cells or plate(s) are down over a long time, you will never get it full charge any more and have to buy a new one.