Weak idle on low battery after sitting

Twice after letting my 83 kz440 Ltd sit for a week it has had a very weak idle, it originally starts fine and then slowly goes down until it stops in under a minute or two, runs fine if reved up slightly.  First time it happened I charged the battery up and it ran fine after and the second time happened today and I just rode it choke on and it was fine, turned the choke off before leaving my neighborhood and it would idle then.

The battery is a gel and maybe a year and a half old, but it did spend a year of its life on a trickle charger while I was working on the bike.  I did have to replace the regulator rectifier and it does read a little lower than spec, but hasn’t had any issues keeping the battery charged when ridden more regularly.  I still need to pop the cover for the stator off and give that a closer inspection, I have read corrosion on the connectors can cause issues.  I considered a three phase stator, but it seemed more expensive than it’s worth when the direct replacement regulator rectifier was only ~$20.  Worth noting I still haven’t vacuum balanced the carbs, but it runs well normally as far as I’m aware, I’ve ridden it 200-300 miles since getting it road worthy.

I was wondering if any of y’all that know these bikes a lot better than me have any insights.  Does it sound like it could be a sign of deeper issues(maybe coils?) and cause for concern or just the charging system/battery being weak?  I’ll probably start actually putting it on a a trickle charger if I haven’t ridden it in a few days as the easy solution.

I would start with getting the carburetors properly tuned. That includes fuel level, idle mixture, synchronizing and idle speed.
If you suspect some electrical problem, I would recommend getting the fsm specs,  Wookie58's trouble shooting page and a decent multi meter and find out if there is a weakness or failed component.

a healthy gel battery should hold charge for several weeks, you may have a drain on the system. If you have a multimeter switch the test lead to the 10amp position disconnect the the battery ground and connect the meter (on the amps setting) between the ground lead and the battery. Do not turn the ignition on - the reading should be zero, any more suggests a drain

Check to make sure you are using the correct charger.  My electrician friend explained that I killed an AGM battery last year because I had it on a cheap trickle charger over the winter.  Apparently the AGM's are more sensitive to fluctuations in charging voltage, where a lead-acid battery will not be affected.  Since I'm generally electrically ignorant (sorry Wookie!), it made sense to me.  

Wookie58 wrote:

a healthy gel battery should hold charge for several weeks, you may have a drain on the system. If you have a multimeter switch the test lead to the 10amp position disconnect the the battery ground and connect the meter (on the amps setting) between the ground lead and the battery. Do not turn the ignition on - the reading should be zero, any more suggests a drain

Came back at zero amps with ignition off and 6.5 amps when it was on


I think I was mistaken when I said the battery was a gel, it's a sealed AGM, and I thought that implied gel, but after reading more I'm not sure.  This is the amazon listing of the battery  www.amazon.com/dp/B07BLQZG19?ref_=ppx_hz..._asin_title_0_0&th=1

I do have an old battery tester that was my grandfather's so I gave that a try and the battery did come back weak, so maybe the battery is just cheap and dying already at only 475 days since purchase.
 


I brought the bike into my garage/shop area, I think I am going to pop the stator cover off and clean the connections and run the testing procedure on it again.  Also planning giving it a 2nd oil change, balancing the carbs, and checking their fuel level while I have it in there.

sf4t7 wrote:

Check to make sure you are using the correct charger.  My electrician friend explained that I killed an AGM battery last year because I had it on a cheap trickle charger over the winter.  Apparently the AGM's are more sensitive to fluctuations in charging voltage, where a lead-acid battery will not be affected.  Since I'm generally electrically ignorant (sorry Wookie!), it made sense to me.  

It's a Stanley BM1S and looking it up online it seems to be a fairly standard 1 amp charger and maintainer as far as I see, online says its compatible with agm, gel, and wet.  I just found it in my late grandfather's stuff so I've never actually looked it up until now.