A 3 month old battery loses its charge with 15 miles

Hi there folks.

i bought a new battery in April 2026 for my 1981 KZ440 LTD. The battery model is Yuasa AGM  Motorcycle Battery YTX7L-BS

it took around 5 hours to charge, after being left in the unused bike, charged after receiving it in April then installed. After an 8 mile trip into town the bike stalled on low revs. I got it home after hill starting a couple of times.

it appears that the battery is simple a dud, however I’d like to test it to confirm, as perhaps there is a wider electrical problem that might be draining the battery while it is unused.

id be grateful please for any advice about checking the integrity of the battery and/or checks I can make on the bike to see if the cause of the battery drainage lies elsewhere. 

very many thanks. James

Use a volt meter set to DC and jumper across the battery to read voltage.  Start up the bike and rev to 5000 rpm, to see what the charging system is doing.  A proper charging system will charge the battery at about 14 - 14.5 VDC at 5000 rpm.  Chances are high that you are not getting much if any charging.

Thanks Nessism.

I’ll recharge the battery and do that.

in the meantime, would a good battery 3 months old, without any charging, last more than 15 miles of typical riding? I would have thought so, making me think it’s a dud battery, but I may be wrong. 

thanks again. 

Jimbo68 wrote:

Thanks Nessism.

I’ll recharge the battery and do that.

in the meantime, would a good battery 3 months old, without any charging, last more than 15 miles of typical riding? I would have thought so, making me think it’s a dud battery, but I may be wrong. 

thanks again. 

Probably not to be fair

Battery charged. I won’t get a chance to start her up and measure the voltage until next week. 

I’ll be back in touch then. Cheers. 

Wookie58 wrote:

Jimbo68 wrote:

Thanks Nessism.

I’ll recharge the battery and do that.

in the meantime, would a good battery 3 months old, without any charging, last more than 15 miles of typical riding? I would have thought so, making me think it’s a dud battery, but I may be wrong. 

thanks again. 

Probably not to be fair

I have a crappy story for this. My 1000 csr had the stator go bad on it. I didnt realize it yet and went to my brothers work 8 miles away to pick up something because he apparently owns the whole garage and can take stuff wherever he wants... 

Wait, where was I?  Anyways I had the bike idling in the parking lot and when I put on the brake to mount the bike it died immediately. I ended up getting my bike jumped by a random neighbor after trying to push start it a lot.

I started driving it hope and it lost power really bad to where I can only imagine it barely had any spark where i was almost full throttle. 2 miles from home I got stopped by a stop sign and the bike died again.

This time I wasnt so lucky and had to push it the rest of the way home with sticky front brakes on a hilly back road... I dont want to have to do that again. All to say I made it maybe 8 miles on a battery with an unknown charge and about 5-6 miles on a very dead battery.

Yeah, that's one reason I have a digital voltmeter on my dash.
If my voltage drops below 12.6v while riding, I can start making plans.
I had this happen once and figured I could make it home if i didn't stop.
A stator wire had come loose.
If I didn't have the gauge, the bike would have died miles from home.

I got this idea form Allen Millyard

 

After a full charge and 5 days passed without switching the bike on, I measured 13.5V before starting it up.
at 5000rpm I measured the same voltage: 13.5V, so if it should measure more I assume it is not being charged as you suspected.

can you please advise what I should look at next?

thanks again.