Like Bill2099, I went through the same thing with my 150cc GY6.  My problem was an intermittent shorted tether kill switch.  Having a quad that starts sometimes and not others is frustrating.

Its time to start using the voltmeter.  While cranking, what voltage do you measure on the kill switch wire to ground?  Measure using both DC voltages and AC voltages (the actual waveform is a combination of both).  When measuring AC voltages be sure and measure them with the leads connected both directions.  Report both readings if they are different. (I know this sounds strange, but many AC voltmeters don't measure right when there is superimposed DC voltages on top of the AC voltages.  The cheap Harbor Freight meters for less than $5.00 are a good example of this).

The voltage on the kill switch wires should be substantial.  Be careful - a working quad has high voltage on these lines while cranking so keep your fingers out of the circuitry.

If you have a large voltage here (exactly what that is depends on the CDI design) then the stator power winding, front end rectifier of the CDI, and kill switch wiring are all OK.  That leaves the Stator trigger connection, SCR firing section of the CDI, the ignition coil and spark plug (and all associated wiring).

If you have no voltage here then we need to look at Kill switch wiring, CDI front end and Stator Ignition power winding.

Report back what you find and we can go from there.  

Oh man... I don't know where to post this but I kind of have a similar problem.

I have a 49cc chinese made quad and there's no spark at all. I've asked all over the place for an answer to why I'm not getting a spark. I've read all these posts too. This person even replaced the stator. I'm afraid of spending money and getting no change in results.

What I did was I took my ignition coil up to this motorcycle shop and got it tested. He said it passed and showed me that it was making sparks. My spark plug seems to look and work good as well.

I bought a new CDI rev box. Worked in my cousin's 49cc atv. That wasn't the problem though

I checked all the wiring. Everything looks fine. The only thing I'm afraid it'd be is the stator. I have five wires coming from it. I figured I'd bring it to the motorcycle place and ask if it could be it. He said that he's only sold two of them within the year meaning that they're hard to go out. Still, I'm afraid that it could be something else IF I bought the stator some where.

I read here that it could be electrical. What I'm going to do is check the handlebar kill switch to see if it's wired inside correctly. I had a feeling it'd be that from the beginning, these quads are poorly made so I'll check that.

I hope it's not the stator though. I don't mind replacing it but I'm not in the mood to buy something around $50 and it'll not be it.  

Actually, I found my problem. I read on another forum that I should unplug the black/white wire from the CDI box (row of three, middle wire) and see if there's a spark. If there's no spark afer that's removed, that means the stator is bad. If there's spark, that means the emergency switch is bad. Luckily, my switch was bad. I got my atv running at 10pm and drove it down the street a few times. Real fun.  

Kill switch wiring rears its head again.  I'm glad you got it working  

lol Thanks. How could I keep that kill switch connected? Is it just a bad wire or what? And is it fine that I leave it disconnected? I covered the wire with black tape and left it alone haha I figured why not. Plus I have a whole new wire kit for the atv if need be.

Come to think of it, when I tried pulling that safety plug from the back so the engine dies if you fall off, it's slingshots back at you. I don't want that crap happening to me. I think that'd hurt more than falling, rolling and scrapping some skin. I live on the dangerous side.  

The kill switch connection to the CDI is shorted to ground by a switch to kill the engine (or switches if you have more than one way to kill the engine).  It is open (not connected to anything) for normal running.

You can leave the kill switch disconnected but you still need some means to shut the engine off when you are done riding.  On my ATV that "kill" connection is done by one pole of the ignition switch.

For safety sake I would not disable the thumb activated kill switch on the handlebar.  If something goes really wrong (like the throttle stuck wide open)you really want to be able to shut things down without letting go of the handlebars.

I also have a safety tether kill switch.  I never tie it to me when I ride. If it ever breaks again I may just take it out.

eBay is a really good place to find replacement parts.  

So how can I fixed that? I don't really know if the handlebar kill switch works or not. I haven't tried it yet. I've only driven it once so far so the only way it's went off is when the throttle just goes off by itself.

I have two ways to kill the engine. On the handlebar and what you mentioned, that tether on the back if you fall off. I assume both are connected to that same wire.  

Ah crap. I have an ignition obviously, with a key and all. Can't I just turn it off like that?  

Eh. I never post two in a row, let alone three times.

I plugged in that black/white wire and disconnected the teather switch. It works now. I don't know why it didn't before. Well I drove it down my street back and forth once, stopped at a friends house and he pointed out that it was leaking gas through that tube from the carburetor. The gas tank went empty, obviously stopped leaking. I poured the gas back in and it was leaking again. I'm guessing the carburetor broke or some junk. It was closed, opened half way, opened full, and still leaks. The atv does start up while it's leaking.

Any clue what this could be?  

I can't help on the carburetor leaking problem.  My engine is different. My first thought was whether it was leaking from the hose from the gas tank to the carburetor or out another hose like an overflow hose?  Stuck needle valve in the carburetor?  Anyway, be careful with fuel leaks. Gasoline fires can be deadly.

It looks like you and I both have three ways to kill the engine:  Ignition switch, thumb switch on handlebar, and tether safety switch.  Any of the three can kill the engine.  All three must be working (or the wiring disconnected to any that are not working)for the engine to run.

Really, you need to think about getting a volt/ohmmeter.  Harbor Freight puts them on sale regularly for $2.99.  They aren't top notch, but they work fine for measuring DC voltages and resistances.  AC voltages are iffy.  I have several.  They are almost disposable.  

Well about the caburetor, it's leaking from the hose that's coming out of it which goes to nothing. I assume it's the overflow hose. Maybe it is a stuck needle but I have no clue how I'd fix that. I did read something about a float as well. I'm not good with caburetors. I pour gas in, it all pours out from the hose.

Hopefully I won't have to replace the caburetor because I can't find a replica on ebay.

About the safety switch on the back, the teather, it's disconnected. I guess that was the problem. I could be wrong since I only disconnected that and everything works fine now.

Thanks for your help with this. I'll figure it out eventually. I just hope I don't drive it at the wrong time and get pulled over by the police.  

I hate these damn chinese things, I will never buy another one. Only Hondas and Yamahas for me for now on.  

i had a lot of problems with then china made atv's
if u have spark but it will not run try swapinng the cdi box for oone that u no that works  if that dont fix it try swapping the iginition switch and make sure the wiers are the same in the plugs i just happen to be a dealer for them and of the 65 or so i sold i had about 20 or so with bad cdi and ignition switches . if u want a good china made atv try the atv 400 a made buy ODES i bought 1 and not a broblem with it in 2 years of use  

I have a chinese supermoto quad bike dont now if it is 110cc or 150cc i have no spark i have replaced the cdi box the recoil starter and sprayed all the conecters with WD 40 and have checked the kill switch  also changed the spark plug what shell i do.
thanks.  

Look at the 2 CDI's below, pick your CDI, find the kill switch connection, and measure the voltage on that pin to ground while cranking and report back.  If you can't probe in through the back of the connector then use a straight pin to poke through the wire insulation to the inner copper.  There may be high voltage on this line so mind your fingers while measuring.





This point is actually a complicated waveform with both DC and AC components, so measure the voltage on both DC and AC settings and report both.  When measuring the AC voltage measure it with the leads one way and then do again with the leads reversed.  Report both readings if they are different (some meters don't read AC voltage correctly when there is a superimposed DC voltage as well).

This measurement is looking at the ignition system right in the middle.  The measurement results will direct us in different directions toward the problem.  Divide and conquer...