help diagnose possible electrical issue Sento50

[Sento2009]

I bought this 2009 Kymco Sento from someone about 8 months ago knowing he could not get it to run.  I wanted to test my diagnosis skills and see if I could fix it, but  it has now been 8 months and I am still trying to figure out why it wont stay running.

When the battery is fully charged I can get it to start and run. At one point I could ride it for about 5 mins.  But then the headlight started to fade and the scooter died and would not restart. I think because the battery was drained and voltage was too low. 
The main problem is I think the scooter when running is draining the battery. I am getting a charging voltage, but it acts like the scooter is running on battery power. 
The other guy and I have replaced the stator, rectifier and I am still get the same issues.
   
I get 14 VAC at the headlight connection (per manual) when head light is disconnected.
I get 14VDC at the battery.   So I think the charging system is working.

I tested the stator with the engine off and get 2.2 ohm on both yellow and white wires. When the negative multimeter led is grounded to battery neg terminal.

The rectifier tested when removed from the scooter gets 3.7Mohms from yellow to green connection points both ways holding the multimeter probes and 3.6 Mohms with pos probe on white and neg probe on red connection. All other combinations gets Open Circuit reading.

The 5w/12ohm resistor by the headlight tests at 12 ohms.  The shielding around the wire coming out of the resistor was missing.  I put electrical tape to stop it from shorting out.  Then while testing the resistor's resistance, I wiggled the wire and the Ohm reading stayed at 12.  That was my last hope.  I was hoping the resistor was bad.

A month ago I did check the valve gaps and they were ok.  I think it was .04 thou.  I cant remember.

I did check compression test a few months ago.  with the tester screwed into the spark plug hole I only got 80 psi.   But when I used the adaptor that you push into the spark plug hole, i got 120 psi.  So I think the compression is ok.  I think my screw in tester lead was just not getting a tight seal.

I also have taken the fuel line off the carb and try to start the scooter and the fuel flow was fine from the pump.

The only thing I have not checked is the timing, but I do not have a timing light.
What am I missing?

I thought this would be and easy fix. I was wrong. 
TIA!

[Alan F.]

With your meter set to Ohms, test from each stator wire to the bike's chassis then battery negative.

Stator wires should show as connected together, but never to chassis or ground. That would be a reason why it might not be charging.

Test is stator output, after charging your battery back up with a low current, gentle battery charger like a Battery Tender, disconnect stator and start the engine (bike up on center stand) set your meter to 200 Volts AC and measure stator output at idle, then rev the engine, AC voltage should rise with engine speed.

Your Rectifier converts AC to DC, then your Voltage Regulator drops voltage down to about 14 volts.

Shut the engine off, reconnect stator, start the engine (bike up on center stand) set your meter to DC Volts and place your probes on the battery terminals. Measure voltage at idle, then rev the engine, voltage should go up to about 14.6 volts DC but shouldn't go much higher.

[Ruffus]

@Sento. The other guy and I have replaced the stator, rectifier and I am still get the same issues..
Just to be sure: Do you have the right rectifier for this model?
As far I can read of your description, I would claim out a mechanical fault.

I get 14 VAC at the headlight connection (per manual) when head light is disconnected.
I get 14VDC at the battery.
Once you have AC then DC, seems unusual to me, pls check this out.

If there are 14VDC arriving at your battery and charging it, this current must logically dissapear somewhere, when lights dim and motor stalls.
So, either this current is not constantely charging or there is somewhere a user.
Could be a short, a broken cable, or simply your "new" battery is faulty too.
Take out all fuses except necessary to start, run, put next in it, see what happens...run put next one in it and so on....
Pls try in this direction and maybe give us a feedback.

[Alan F.]

Ruffus makes another point, there may be a short elsewhere in the system. Do all lights, turn signals and horn work? Anything not working might potentially be a place to look for a short circuit.

Are you blowing any fuses?

[Sento2009]

Success. New cdi came in today.  Scooter started with the  push of the button.  I was only able to run it for a few minutes.  Too cold tonight for a test run. The scooter was running much better than before.  Even the battery charge was14.4 vDC.  Before it was charging at idle at 14 vDC.  I think the old cdi was faulty and drawing more amps from the battery than the generator could supply. 
Thanks for everyone’s suggestions.

[Alan F.]

Good work, I hope you can get out for a ride soon & post back with success!

[Ruffus]

Congrats!!!👍👍

[Sento2009]

Well I spoke to soon.  The CDI did help.  the scooter starts right away, but I still have a battery drain while it runs.   I tried to test drive it and when I turned the throttle, engine bogged and did not go anywhere.   
So the scooter does idle and start if battery is charged.  but if the scooter runs a little while the battery drains and once battery goes below 12.8 volts scooter will not start.
So I still think it is an electrical issue not a fuel issue.
Does any one have real ohm readings for the rectifier.  I am not getting anything close to the service manual.  Plus I have read that the service manuals readings are not what people are actually getting.

I am running a new amazon.com (knock off) stator and rectifier.  Do I need to replace them with OEM parts. The sento is not that sensitive to what parts are used, is it?
Any suggestions are welcome.

[Alan F.]

I've edited all unnecessary wording from my reply#1 above. Perform those tests and forget about the resistance values you'd find on a rectifier, it's either doing its job or it isn't.

You need to know if your stator is putting out AC on all of its leads first.