when first started it has a nice blue spark then not even a minute it loses all spark. what could be the problem. changed cdi box

 

That's a strange problem. What changes over the course of a minute from startup? The only thing I can think of is engine temperature. That points to the stator, which is inside the engine covers. I don't think the external modules (CDI & ignition coil) would heat up that fast. The spark plug heats up pretty fast too.

How long do you have to let the quad sit before it will start again?

Do you have a voltmeter? Does you CDI look like this?

 

well its like this i take the spark plug out of engine and keep it hooked up to the spark plug wire and touch ground and then turn over engine and the plug produce a blue spark but not even 30 secs. the spark just dissappears just like a switch was shut of. but when you turn it over sometimes it will spark but rarely.i usuall go check it the next day and the spark is there and it all happens all over again i lose the spark. i changed the cdi box.did not make no difference. unhooked the kill switch wire from cdi box. still no difference. the cdi looks like the pic you have.and yes i do have a voltmeter. please help

 

still need help any body willing to help

 

Bad coil?

 

well idid lots of checkin this thing out and cleaned up plugs, stator,and it seems too run now its weird but now it seems to backfire a bit in the airbox. anybody have any suggestions. help someone

 

For the following tests be sure to do your measurements while the ignition system is acting up and not generating spark. It is absolutely critical that you don't accidently take a measurement while the system is generating spark (i.e. working) or you will be making conclusions from erroneous results. This will send you right down a dead end path. Because your problem is intermittent it is much harder, and you have to be vigilant about details.

I would first do the spark test (verifying no spark), do each of the measurements below one at a time, and then do the spark test again so that you've verified the ignition system isn't working both before and after each test below.

AC Ignition Power:

While it is acting up and not making a spark, unplug the CDI and hook a voltmeter to measure AC volts from the AC Ignition Pin of the wiring harness to engine ground. Crank the engine and measure the voltage. You should have about 80 volts AC at cranking speeds. Report your actual measurement back.

While the engine is stopped switch over to measure ohms. Measure the resistance (in ohms) from the same pin (AC Ignition Power) in the wiring harness to engine ground. You should see about 450 ohms or so. What do you measure on your quad?

Ignition Trigger Pulse:

While it is acting up and not making a spark, unplug the CDI and hook a voltmeter to measure AC volts from the Ignition Trigger Pulse pin of the wiring harness to engine ground. This is a much lower voltage so set your meter to read less than 1 volt full scale. Crank the engine and measure the voltage. You should read 0.3 to 0.5 volts AC at cranking speeds. Report back your actual measurement voltage.

While the engine is stopped switch over to measure ohms. Measure the resistance (in ohms) from the same pin (Ignition Trigger Pulse) in the wiring harness to engine ground. You should see about 140 ohms or so. What do you measure on your quad?

What these tests are doing:

The CDI is powered from a moderately high voltage AC power source coming off the stator. It is roughly 80 volts at cranking speeds, but is rises with engine RPM to several hundred volts AC when the engine is running at speed. This power supply voltage is rectified to DC and stored up on a capacitor until the ignition trigger pulse (also from the stator) tells the CDI to dump the stored energy on the capacitor all at once onto the ignition coil primary. The ignition coil steps up this voltage to 10,000 volts or more and fires the plug.

Without the power supply voltage to the CDI, or the trigger pulse, there will be no spark. Since both these things can be measured you can tell if the stator is doing its job or not. The stator is difficult to change compared to the CDI or the coil. So its nice to eliminate it and get it out of the picture if it isn't the problem.

Ignition Coil Primary and CDI ground Continuity:

While you're set up to do testing (and you have verified you still aren't getting spark), measure the resistance (in ohms) of the Ignition Coil pin of the CDI wiring harness to ground with the engine stopped. You should measure 1 ohm or so.

Measure the resistance of both Ground pins of the CDI wiring harness to ground. They should both be zero ohms, unless you only have one ground wire in the harness in which case only that one wire should be zero ohms.

 

ok i played with this quad for days again LYNN and this is what i have done i changed the coil put some new ends on some of the wires because they looked kind of weak. so i tried starting in then and it works great. drove it for about 45 minutes straight and drove it hard then i would stop it then start it again runs good. then the next mourning i try starting it and guess what no spark none what so ever. what is goin on! so did some tests with multi meter and this is the weird readings i got----50 vac at 200 setting
ignition trigger pulse-0.1
ac iginition power-.509 ohms @2k setting
ignition trigger pin-150 ohms
ignition coil pin-.019 @2k setting
spark plug wire-1.0ohms @2k setting

then i plugged all plugs back into the cdi box and it started again just like nothing ever happened and ran very good so iwill try starting again tommorrow and see what happens. please let me know. what could be the problem with this thing. it has a mind of it own.

 

I'm assuming the following: "ac iginition power-.509 ohms @2k setting" means 0.509 Kohms (0.509 kilo ohms, or 509 ohms)....

The problem with your measurements is that it worked just fine when you plugged it all back together. Thus all your measurements are suspect because you don't know whether you took the measurements when the quad was working, or not working. Intermittent problems are the worst kind. I wish it wasn't so but that is reality.

First thing in you measurements that raises an eyebrow: You measured 0.1 volts AC for the timing/ignition trigger pulse. That could very well be your voltmeter reading a little low - it is down at the lower limit of measuring for a lot of meters - or it really could be low voltage from the pickup coil.

Couple that with a recent post where someone was able to adjust the timing trigger pulse voltage by moving the pickup coil closer to the flywheel. In that case they went from no spark to good spark with a simple adjustment. It's worth a try. The pickup coil is outside the flywheel so it is just a matter of removing the side cover. You may be on the edge of working / not working. If this is the case I would think that you would never have a problem with the quad just suddenly quitting without warning while just tooling around the countryside. Rather I would expect that the quad would run fine till you turn it off then it won't start again. This would be because the generated trigger voltage is proportional to engine speed - and cranking speed is about 600 RPM versus 1500 RPM for engine idle.

You've changed the CDI and the coil. timing trigger pickup coil, stator, intermittent kill switch grounding, and wiring are all that is left. Maybe the spark plug (a long shot).

Second thing in your measurements that raises an eyebrow: "0.019 on the 2K ohm scale" isn't right. I assume that means 0.019 Kohms (or 19 ohms). It should be be more like 1 or 2 ohms. Try a lower scale and see if it makes more sense.

Intermittents are tough. I'm impressed with your technique and thoroughness so far. Keep going - you'll solve this.

 

these test were all done when there was no spark at all. but i will do all the tests all over again.keep u posted