Need help with a Kymco starting issue.

Picked up a Yager 200i (fuel injected) scoot with less than 1000mi.
Previuos owner had problem with battery going dead so put a tender lead on it.

Picked up scoot and dealer put a new interstate battery in it.
Battery lasted 5 days then would not start w/o a tender hook up every night.

It was undersize so i bought a Scorpion yt12a-bs agm 175cca (biggest that would fit).
Worked again for a few days and then dead.

so i checked the battery today.
engine off it sits 12.5v
engine on it registers 14.04v from idle to being reved. never goes above or below that.
is 14v enough to be charging?

when i have a charged battery (from a tender jr) starts great.
if i turn it off, then turn key/lights back on (but no start)
the battery drain down to 10v in about 45 secs and then holds there in voltage but will not start.
this seems very quick to drop that much in voltage so basically I have seconds for a good start...then no reserve.

this is a new battery (scorpion yt12 175cca) and replaced another battery that was a week old and was not starting.
any idea what is going on here? or what i should check next?
i'll take battery to parts store and do a load test just to confirm but i don't think it's a battery...something in the engine is causing a massive voltage draw.

i've checked all grounds/positives, cleaned connections and di-electric greased. all connections were factory tight. fresh oil & gas, new iridium plug, led lights in all except headlight. headlight does come on with key, not after bike is started like other machines. the light the under seat storage is completely disconnected.

if i connect up my lithium jumpstarter it fires up like a boss. when running, runs like tops.

i'd put a lithium battery in this scoot, but I have a deeper issue I have to deal with???

Sounds like a current draw when the bike is off, could the ignition switch be leaving the computer on when the key is off?

The only way to confirm a CURRENT DRAW with the SWITCH OFF, and its AMPLITUDE, is to connect
an AMP-METER in series with the battery NEG. cable. Anything more than a few mA leak is not
normal (looks like you have a MASSIVE one - or two bad batteries in a row (improbable)).

Once you have determined that there IS a leak, disconnect -successively- all the electrics (with the
Amp-Meter still there, to discover which is causing that leak. Often, it is a diode in the Rectifier, but
who knows...

If no leak, check all the grounds for PERFECTION, no less.

Thanks!
My tester will operate in either
.2amp or 10amp mode depending on which connector the positive is plugged into.
Which one?

Tonight I fully charged the battery and it tested at 12.6v. in the am I will test again and see how much it drops. This should give me some working numbers.

Grounds all are cleaned & greased.

That batt seems low, usually they are fully charger at over 13v closer to 14v just my .2c worth

Begin with the 20 amp scale. If that blows your tester's fuse, you're having a BIG leak !
And as 50grit said, 12.6V is very low for a fully charged new batt (13V plus is the norm right after
charging them)...

If there's a load on the battery after charging it could read that. May need to unhook to read true battery voltage. Start high on the current reading and work your way down.

Good luck

It seems if you had a good battery a voltage drop like that would result in something smoking.
FWIW I had a lithium iron phosphate battery on my scooter that I managed to kill by overdrawing it. It would charge to over 13v but then lose charge to ~10.2v and stay there indefinitely (I have a voltage meter installed on the bike), not enough to start the bike. I replaced it with a lead acid battery that works great, ~12.5v when fully charged.

I took the lithium battery apart, one of the four cell pouches was ballooned, when I punctured it with a pick ax no reaction, the other three smoked as expected.

Even if it is unlikely that two batteries in a row are bad if you have a 3rd battery around I would give it a try as long as you don't find a short somewhere causing the drop.

I have a 10 amp scale is my max.
Guess I'll start there and see how the fuse holds.

Maybe those deep discharges on the battery damaged it? I did not test it when I got it new 2 weeks ago however. Maybe sulfation? All I have is a tender Jr, so no desulfation mode.
Do any auto parts stores have desulfation modes in their charges they offer?

Why does Yuasa (& others) say 12.6v is fully charged?
http://www.yuasabatteries.com/faqs.php?action=1&id=30
I'm not reading where 13v +/- is where a fully charged battery sits.

I'll check that too.
Last night the battery connected to scoot was reading 12.6v.
Heading home now, I'll test and see how it reads after 10+ hrs.

13.0-13.1V will show with a new batt, RIGHT after it has been fully charged. A few hrs later it will
drop to around 12.8V. My 10 years old NH80 batt wont show more than 12.5 volts an hour after a
five-hr/ 1amp charge, but is still good enough to start it easy -but then a 80cc 2 strokes is not that
hard cranking...
Yuasa says 12.8V, an hour after a full charge, is perfect.

Ok what's odd here is the battery now sits right at 12.5v and cranks up & starts great.
On other days it would barely start if sitting overnight w/o a tender. More confused than ever :-(

Will test amp draw asap.

ok brought my neighbor in to test some things.

bike started strong 3 times then died on the 4th

we are guessing when the engine starts it has a ground fault to the frame and dumping juice. i do not have an overnight battery drain issue.
this does not happen every time however???

this is the run down:

-battery holds 12.5v when sitting for days - good
-scooter charges at 14v consistently - good
-on a 10amp scale, the negative wire & negative battery post draws 0.01 key off - good
-on a 10amp scale, the negative wire & negative battery post draws 5.4 amps key on?
-continuity is 0 on the negative battery side to all frame points and engine - good
-continuity is 0 from positive battery to starter relay battery side - good
-no continuity across the starter relay when off - good
-continuity is 0 from the starter side of the relay to where the possitive attaches to the starter
PLUS is 0 to all ground points on frame/engine??? Is this normal??? - not good???
-small voltage is seen on the frame ground to negative battery when trying to start? not good?

the big ? is there continuity on the hot side of the stater to the frame/ground?
logic tells us no as those 2 connections should be separated.

do I have a bad or inconsistent starter?

thanks!

There should be a weak Resistance (what you call 'continuity') between the starter (+) and ground .
This represents the starter winding's Resistance, through the brushes and commutator. Most
manufacturers don't take the pain to provide information on its exact value, so you'll have to
dismantle the starter and have a look at its brushes/commutator (there should be NO continuity
at all between between any of the commutator's segments and the starter shaft; the resistance
between any segments should be very low + equal everywhere; the brushes + commutator
must look good and CLEAN.

An 'hesitant' starter will usually show a very bad looking commutator surface, which can be cleaned
with strips of sandpaper (+ brake cleaner). Then the resistance readings must measure as said
above. If the readings look ok , give that starter a try ---most of the times it will be fine.

I have seen low mileage starters with very bad looking commutators working just fine after a simple,
methodical cleanup.

Thanks. I'll probably just pick-up a new starter (if that's my issue) for $50 or so.

So what I'm understanding is continuity is expected across the + and - connections of a working starter and this is not an issue.

My problem in the end is when I go to start this engine. It either fires just fine or stalls (on the starter turning), then the starter turns (but weaker), then at this point the battery has quickly lost at least 1.5v and then the FI system does not have enough juice to fire.

This problem causes a fast battery drain & then I have no battery reserve to actually fire the engine.

If I connect my Lithium jumper battery, it cranks up strong every time & pushes past this problem and the motor starts. Every time.

Once running this motor runs like a champ and never miss fires or gives any electrical anomalies.

It's all in the crank and fire up procedure.
My buddy thinks it might be where the starter stops & then cranks from again...

Thoughts?

as above, the resistance of the motor's field & armature windings is so low your meter resolves to zero. I don't think the starter is the problem.

a voltage between frame and ground means the connection is poor (frame to battery)

"the battery drain down to 10v in about 45 secs".... something there isn't right. measure the amp draw with the key off, then with the key on. remove the negative cable from the battery and insert the meter between the cable and battery. make sure you are in the amp settings and the meter cables are correct. as soon as you make the readings, switch the meter plus lead back before you forget. don't try to read the starter draw.... it is far too high for your meter. you are mostly interested in how much draw there is with the key on... shouldn't be more than a few amps. if it goes off scale or blows the fuse I would be looking for a short.... possibly in the rectifier

is there a wire diagram?

a 1000 mile old starter shouldn't be having problems but it is possible. sometimes the bearings or drive gears can get worn or broken & cock off a bit. that causes the starter to jamb up & not turn, which causes high current flow & drains the battery