can stators break down? (aerox won't run over a few minutes)

[shoom]

Hello all,

I have just rebuilt my aerox with a view to getting licensed for the road soon,
And everything is back together, it has fuel, new plug, I checked the compression, it's 120psi cold or hot, I've checked for leaks in the crankcase and I've tried 3 different CDI units and the same thing happens with all 3. 
At this stage I'm thinking the Stator has to be the only thing left suspect.. Can these things go bad? I'm thinking maybe a solder joint is very loose and it contacts enough to work when cold, but loosens up when the engine gets some heat and the circuit is lost?
It will run for about 2 or 3 minutes and just die suddenly with that moaning sort of noise, and will not restart until you wait for it to cool down several hours. And I've tried another completely seperate known good phbg 21mm carb and the exact same thing will happen, it's not flooding either as I have pulled plugs many times. I'm just throwing this out there as two brains are better than one yes?
I posted a video of the sparking, it's a little weak to my eye and dances around off to each side, whereas it should have a fatter 1mm + wide bolt yes in the centre? I can only think by elimination that the stator is the last bad thing.. 

Tell me what you think..

Kind Regards,

Tom S.

[aeroxbud]

Have you checked the coil? Section 10 49ccscoot.proboards.com/thread/647?page=1#8068

[90GTVert]

When are you checking spark? If it runs for a bit and dies, then I would want to check spark soon after the engine died, while it still won't start. If you want to check spark strength, get an adjustable spark tester or take an old plug and cut off or bend the ground strap all the way back to make a large gap. It should be able to jump that and still look white/blue/purple. If it will do that when it won't start, you should be able to eliminate the ignition system as a likely cause.

[geoffh]

Compared to my Yamaha spark yours is in rude health,of course Yamaha stators can fail but it,s far from a common fault,I am with aeroxbud and would look at coil and HT lead and plug cap.

Geoff

[snaker]

You also might want to consider the auto-choke / carb circuits.
The time you give would be about the time the auto choke closes off. If the carb is plugged then the autochoke may be keeping it running till then.

[ThaiGyro]

Hey shoom...what the boyz said is good, and you might consider checking your "pickup" coil. (Hall effect coil?) I have had many of those fail from heat on race bikes and hot temperature riding. Often they will start, then overheat. Just a thought...

[GrumpyUnk]

I think there is a post where a LED was used as the indicator for the pickup coil. If you have an AC CDI, you can put a VOM on the 'power' lead from the stator to the CDI and crank it over. No power==no CDI worky.
A stator has at least 3 windings I can think of. Most have two legs used to generate power to run lights, etc, and one to generate power to operate the CDI. DC CDI will not require that winding.
Two modes of failure that pop to mind are 1)failing insulation on the windings/leads and 2)solder joint problems. The lacquer used to insulate the windings can fail due to vibration, and can cause shorting or reduced output. The insulation on the leads can chafe or fall apart(hecho in ...), allowing shorts to reduce/kill the output.
In most cases, the stator lives a good long life if not abused or damaged by external forces.
tom

[shoom]

It seems like the problem I am having is a common problem amongst aerox owners.. I see a couple of guys have even gone as far as to replace the entire ignition system , backing plate, flywheel etc and still have the problem. Probably why many bikes get parted out lol
i'm thinking maybe the contact inside the actual key switch that sends the power to the cdi / coil might be dirty. A pig to get in there seeing they use those bolts with the heads that break off to hold the switch to the frame. I will try sending 12v directly from a charged battery down that wire instead and see what happens.. I hope we can solve this for the community.

[dodgerover]

Have you checked for a spark after it has stopped?

[GrumpyUnk]

Rather than mucking around with the ignition switch, why not put a test light onto the B+ input to the CDI when the engine quits working? Two or three minutes is not likely long enough to get electronic things or ignition switches hot enough to fail. Ones that are 'engine mounted', such as the pickup, could be more readily heated by conduct with the engine parts. OTOH, the pickup is right there next to the air cooling blower.
I would be checking the pilot jet in the carburetor and the mixture needle & passages. It almost sounds as if the idle circuit is not working, and you are running on the byvalve(choke) system, and when that cuts off, there's nothing there to run the engine with(no fuel). You could try a squirt of fuel or starting ether sprayed into the inlet side of the carburetor(two t's for you). If it is lacking fuel flow from the idle circuit, the ether or a squirt of fuel should let it run for a few seconds.
tom

[shoom]

Think I have found my problem.

I checked the black wire with the white stripe that goes from the ignition switch to the CDI at the plug, and I am only getting about 7 volts on a fully charged battery. This should be the full 12 volts right?