I have a Motorxtremes ATV.  The spark is very weak.  When .005" from a ground there is a small spark, but not enough to jump the .025" gap.  Before the plug comes the coil, before that the CDI, before that the magneto.  Here is the diagram,  http://motorxtremes.com/pdfs/yatv_wiring.pdf

I saw somewhere here a note about checking the tail light wiring.  I will do that.  As I recall, it's not working.  Have only put about 15-20 hours on the unit.

I have a new coil and CDI.  The new CDI does not help.  I will try the coil again.  Since I first tried it, I found some loose connectors.  In fact, to those with a similar unit, the wiring harness is poor.  Many loose terminals; terminas crimped to the insulation instead of the conductor, etc.  

On the diagram, what is the LW wire on the CDI?  BY feeds the coil, BW is the kill switches.  They are "open" so it's not grounded.  BR is the charge off the magneto which should charge the capacitor (30V open circuit).  G is ground.  What is LW and what is that small component on LW down near the magneto?  

so many different chinese atv's.
almost impossible to know without looking at it myself or seeing a schematic for the atv.
if you have a good wiring schematic/diagram post it or email it to me and i'd be glad to figure it out for you.

you should have at least 2 wires running to the ignition.
3-4 wires coming from the stator depending on the design.

your coil power lead and ground lead should come from the stator. the power lead should be constant, while the ground lifts to cause the coil to intermittently spark.

if you have a weak spark then stator is at least working that much.
are the contacts for the staot and magneto rusted or dirty?

clean them see if that fixes the problem.
if not i would venture a guess that the stator is going bad.  

wolf1 - see the link in my original post.  So the stator is probably inside the engine cover?  5 wires come from inside that cover - LW, G, BR, Y, and Y (near the bottom - center of that diag, around the magneto)  

The tail-light bulb is missing. I don't think that should cause the problem.  I'll put in a new bulb and see what happens.  

Doh!!  i don't have a clue how i missed that link.??...

anyrate i looked and couldn't find a wire marked "Lw"
but i did see one that did appear to be marked "Lv"

it came out of the cdi box and ran down to the pick up pole. magneto/stator contact.
(the little square thing on the end)

it is between the kill switch and the magneto in the diagram at the bottom.

but it is the pick up for the magneto.

no the tail light shouldn't affect it at all.  

I think those "V"s are meant to be "W"hite.  LV is actually a blue wire with a white stripe.  I keep it in my head as lavender (blue) and white.  But you only find that out when you look at the wires!!

So by my definition, LW is then the CDI to pickup pole you noted.  What does that do?  

Where does the energy come from that creates the spark?

Since I have a very weak spark, what's the likey cause?  There's not enough juice to get that spark across the .025" gap, but there is a tiny spark if the gap is about .005".

Those 5 wires shown around the magneto are inside the motor cover.  I probably need to pop it off and see.  

Oh.. is there any voltages I can measure to help narrow down?  With an open circuit, there is 30VAC on BR at the CDI (open circuit.. not plugged into the CDI).  I don't think I measured anything on that LW.  

ok the power for the spark comes from the battery and on some chinese models it's governed by the cdi box,
on other more simplistic models it comes from the a constant power lead from the magneto.

the coil has power to the postive lead always, and the spark happens when the ground is lifted.
so it lifts constantly in time to the engine via the magneto.

when the power to the coil postive lead is weak or non existant then you lose spark or get a weak spark.

the first place i would start is to remove the cover from the magneto..(if your clutch basket is on the left then your magneto is on the right, vice versa.
most commonly the magneto is on the left side of the atv as you sit on it.

the wires should be coming out of the cover.

check it to see if the magneto has beome rusted at it's contact point or if the pick up piece is rusted on it's contact point or both.
this is real common to happen on the chinese atv's because they don't really seal off the cover well.

if it is rusted or covered with mud, dirt etc.. take some 320 grit finishing sandpaper and lightly remove the rust, if it is muddy then clean it with a brush.

it if is fine then i would look into the stator being bad.
there are tons of different chinese atv models so it be hard to venture what the voltage output or even ohms should be.  

the "lw" wire runs down to the pick up piece, as the magneto turns it has a magentic contact on it that lifts the ground for the coil everytime it passes the pick up piece.

the stator under the magneto passes voltage to the rectifier which in turn passes a constant positive charge to the power wire of the coil and other components.  

OK, this has me stumped.

There's only about 15 hours on the unit.  I pulled the cover and it looks clean inside.  There are 2 coils of wire.  One with the white and yellow lead that goes to the rectifier, and the other with the black-red (BR) and green (G) leads which runs to the CDI.  The pickup pole has the blue-white (LW) lead which also goes to the CDI.  It all "looks" OK, but I really don't know how to test it out.  

Motorxtremes send me a new coil and CDI.  I replaced the coil and used the old CDI - does not work.  I replaced the CDI - does not work.  I even tried with the old coil and new CDI - does not work.  I only get a weak spark at about .005" gap.  There is no spark on the plug at the .025" gap.  

There is 30VAC coming off the BR lead when I disconnect the CDI.  

I have a charger plugged into the battery so there's good battery power.  

On both ignition coils there's no resistance between the G and BY leads.

I'm confused how a spark comes from the coil in this design.  It seems to me there are other gounds that would rob the voltage.  I'm confused how the CDI works.  

your cdi is fine  most likely it's your stator.  

the 250cc water cooled w/clutch tao tao(looks like yamaha raptor)runs very hot lots of carbon in tail pipe. runs fine now that adjusted idle it was to low problem is getting it started takes some time now weather riding all day or an hour spark plug and chamber almost look burnt in side i think that this is either a water cooling problem or its a weak starter