Sorry if this question seems redundant, but i've been all over the net trying to type in something that will help me get my daughters quad running.

Machine is 4yrs old, i bought it from a guy 2 yrs ago who could'nt keep it running to get a tank of fuel through it. machine has emblems that say FSN 90cc on the tank. I had a motorcross buddy go through the carb, rejetted it, then we took one of the stainless screens out of the air cleaner, and WHOA baby, thing is actually prety fast LOL!! But now, after 2 yrs, she just wont start, 6 yr old daughter is getting frustrated as is dad.

It's got/getting gas.
I replaced the plug with the NGK plug recommended on here yesterday and still no spark
checked wires inside kill switch housing which look to be instact.
Followed wires from rear kill switch tether and all look good, same as all the plug in connections/fuses i could find and pull apart.

So now i'm GUESSING either a stator or CDI module? how would/does one check the status of the stator to see if it is in fact bad/not working

how would one check to see if CDI (i assume the CDI is the thing mounted to the frame the spark plug wire is plugged into?) is bad?

HELP, i want to get this thing running for her again, so faster i can diagnoise the faster i can buy the parts off flea bay and get it going. Granted i could buy both for next to nothing, but hate poking and hoping since my luck is'nt that good.

Thanks for reading this far, hope somebody can help us  

you need to talk to Wolf1
He is the man
but sounds like an electrical problem.
Do you have an OHM meter?  

oh what type of bike, you say 90cc FSN
is it a Chinese Quad?  

Got a digital multi meter

I assume it's a chinese quad, got a manual and tool kit that had all kinds of chinese writing stuff all over it, it's built very cheaply, and looks like all the other junk quads that get sold for next to nothing everywhere maybe someother foreign country, but i have no idea, searching for FSN did'nt bring anything up, so i'm clueless, and that's what's making me nervious about just ordering parts that "should work"

Hopefully nothing major, she's getting tired of roll'n the John Deere lawnmower LOL!!!  

I feel you
for the most part these engines are Honda clone engines. Most stock engines are really cheap, but even a good one goes for about $350 shipped. So remeber that in a worst case scenerio. I am goint to try and post a link, it may not work, but I will keep trying. It is an entire Honda manual that may be of assistance to you. However if you are in a hurry, I would suggest looking for the part that has the spark plug wire conected to it. It is a box thats wired to the spark plug wire. THIS IS ONLY AN ASSUMPTION, with out further investigating, I can't tell you what to do. Like I said, hopefully this catches Wolf1's attention and he can help you better. Here it goes,
Oh, you can Email me directly incase that is better for you.  

sorry, it did not work, give me a little time, I will get it  

Email me, I will send it to you that way.
Autophysn@aol.com  

First, I don't have a 90cc quad.  Mine is a chinese 150cc GY6 engine made by Hensim.  It is a different engine, so use my experience as a guideline only.  I'm making the assumption that the electrical systems are going to be similar.

The stator is just 3 separate coils of wire.  There are no semiconductors inside, and no moving parts.  There isn't a lot to go wrong here.  You could get an internal short to the chassis on one of the windings, or maybe a shorted turn.  Or an open winding.

The CDI has a lot of stuff inside it.  It is full of transistors, and has high voltage on it.  Placing bets on whether the stator or the CDI is at fault, I would bet on the CDI.  But don't ignore wiring and the ignition coil as possible problems.

As a reference the following two links show a complete wiring diagram of my ATV. Again it will be different than yours, but probably similar enough to be of some use.

http://i397.photobucket.com/albums/pp60/LynnEdwards_photo/Hensim150ccATVPage1.jpg

http://i397.photobucket.com/albums/pp60/LynnEdwards_photo/Hensim150ccATVPage2.jpg

To measure the stator battery charge and ignition power windings accurately they need to be disconnected from the regulator and CDI while cranking.  They both produce AC voltages.  The linked wiring diagrams spell out the AC voltages and winding resistances of my engine.  I would think yours would be similar.

The reason the stator must be disconnected from the regulator and CDI is because both of these units yank the stator output voltages around even when operating normally.  A bad CDI can make the stator output look low or even dead when hooked up even though it is OK.

You can try to measure output from the trigger winding with an AC voltmeter (it need not be disconnected).  You should measure something, but because it is only narrow pulses at a slow repetition rate the AC voltmeter isn't going to measure it correctly.  You could get anything from 0.1 volts to 4 volts depending on the meter design.

Double and triple check the kill switch wiring.  Measure the kill switch wiring to ground with an ohmmeter.  If it is grounded you could crank all day long and get no spark.  During cranking there should be high voltage on this line.  Mine produces +200 volt high pulses at the cranking speed when the kill switch is off.

Lynn Edwards  

We have a 90cc chinese quad.  Can you post a photo?  Maybe someone will recognize it.  We just had some work done on ours.  It was having problems starting and staying lit.  It's running great now.  I will check to see what was done and get back.  

Lynn, thanks for posting up the info!!! I got on flebay and ordered a new coil and a new CDI box, $30 to my door so WTF, worth a shot, and if it still does'nt work then at least i'll know they're new and not 4 yrs old. Hopefully the parts will be here this week so i can slap'em back on and give it a shot. I may even put the old ones back on so i can check the kill switch wiring.

the quad did this to us a few months ago too, no spark. It sat for a few weeks, and one day i hear the daughter tearing around the yard on it??? she said she just tried to start it and it took right off. So who knows, we got our lucky break last time, this time i'm digging in to hopefully prevent this from happening again anytime soon. i'll definately be posting back up with good/bad news when the parts come in. i'll do A/B testing to isolate which component took a dump.

This is the only pic i have on this puter of the quad, i can try to get a shot tomorrow when i get some time.
 

fsn 900c is a tao tao machine.

the wiring diagram under the pictures in my readers rides is identical for it.

you can use that as a starting point and test the wires accordingly.
make sure you are getting voltage from the cdi to the stator. test the coil using and ohm meter, put the red lead in the plug cap and the other on the wire.
for a good coil you should get a reading of approxiamtely 14  

Wolfe, is there anyway you can post a link, I'm having a serious brain fart and am unable to find the wiring diagram that your speaking of

i got the coil in today and threw it on quick, put the old CDI back on, and still no spark, so figure tomorrow if i get off early enough i want to run through the wiring to see if everything seems okay.

Sorry, but just cannot seem to find it.  

The path to get there is sort of weird.  It took me a while to figure it out the first time.

Under the ATV Rider banner at the top of the page you are looking at now are some Blue and white buttons (Features, Reviews, News, Tech (etc).....  Look down one more line underneath this.  There are three red colored links (Forums, Blogs, Reader's Rides).  Click on the Reader's Rides link.

In the upper right on the new page is a search window.  Type in "wolf1" and do the search.  For some reason only two thumbnail pictures show up.  Click on either one of them.

When the big picture comes up you see that suddenly 4 thumbnail pictures show up further down as additional links.  One of them is the schematic you are after.

Lynn Edwards  

Well, got fed up today since i've had zero time, figured i'd drop it off at a bike shop and just let them monkey with it since CDI, coil, and kill switch all checked out here at home, and still no spark. I took it around to 3 shops and nobody would take it....one guy said if i wanted help throwing it in his dumpster he'd help me...which after hitting the nobody will work on it, i almost did.

So got it home, figured, maybe it's something to do with the alarm system, remote start/remote kill that's installed on it. So i pulled the front plastic off, unplugged the alarm and siren, reached up and it popped right off like a brand new one!!! sweet. only thing was the key no longer kills it, the handle bar kill switch still does though.

Had my daughter ride it around the yard for about a half hour, she's happy as a clam. After supper i told her to go out and see if it still fires up...and...nothing again LOL!!! Think it's bout time to just part that thing out, got too much other stuff to do than trying to keep diagnoising this darn thing...she needs a bigger one anyways.  

i been thru this many many times, it's 99% of the time its a loose wire in electical connector or it's the handlebar safety switch stuck in close position.
remove the front plastic again and while trying to start it take each and every wire at the connector and move it around, also make sure the you have no bare wire connectors, sometimes on a single wire connector the plastic thats suppose to cover the connector is loose and falls away from the connector and shorts out.  also check the two wires going to the handlebar brake lever, make sure they are tight on the terimals and that the saftety switch they're going to is not stuck in close position. also remember the brakes must be applied while starting the quad