No spark??

[Rednex250r]

I have a 86 trx 250r and it has no spark and i changed the spark plug wire out and it still wouldnt fire can someone please help me figure out my problem???

[DnB_racing]

Originally posted by Rednex250r
I have a 86 trx 250r and it has no spark and i changed the spark plug wire out and it still wouldnt fire can someone please help me figure out my problem??? here is a pic with resistance readings of components, give them a test and see if this narrows it down

[wilkin250r]

Red, this is where it starts. Very few problems on these quads have a simple explanation like "just change your canooter valve and everything will be fine". Diagnosing and fixing these problems yourself can save you a lot of money, but it requires work. You're going to have to check a bunch of stuff for yourself.

Ignition problems can have a variety of causes, and it helps to understand the ignition system, and you can use the above diagram to help visualize it.

The stator has a couple coils on it dedicated strictly to the ignition system, they are called the exciter coils (the rest of the coils on the stator are power for lights, and they run independently). The exciter coils provide POWER for the spark, it sends power along the red and black wire into the CDI where all the energy gets stored.

The pulse coil is on the outside of the stator. It's a small signal, it doesn't have enough power to actually fire the spark, it's just a timing trigger. It's kinda like the hammer on a gun, and the exciter coil is the gunpowder. The pulse generator also goes into the CDI, but while the exciter coil has only one wire because it uses chassis ground, the pulse generator actually has two dedicated wires for it's positive and negative.

The CDI is the brain of it all. It stores the energy from the exciter coil, and when it gets the signal from the pulse generator, it fires all that energy (a few hundred volts) all at once into the ignition coil.

The ignition coil is basically a transformer, and it takes that few hundred volts and boosts it to a few thousand volts, and then feeds that directly to the spark plug.

Now, here's the thing. The exciter coil, the pulse generator, and the ignition coil are all really simple devices. They're basically just coils of wire in different configurations. How many things can go wrong in a coil of wire? Well, the wire itself could break and no longer conduct electricity, or the insulation between wires could melt and it's no longer a "coil" with multiple loops, it's just a solid chunk of copper with basically one loop (or more precisely, what used to be 100 loops is now only seven loops, or something like that) Since the number of loops is very critical for operation, loops shorting together wouldn't work properly.

That's it. And either of these problems would show up in a simple resistance test using a standard electrical meter. So the test for the ignition coil, the pulse generator, and the exciter coils are just that, a resistance test.

The CDI is a bit more complex, and it can't be tested with a standard meter. The only way to diagnose a CDI problem is to check everything else first, and if everything else checks out fine, try a new CDI.

[C-LEIGH RACING]

Check all the connectors in the wiring harness, that they are clean & fit tight sliding together.
The black wire with white stripe, is the main ignition wire & where it connects to the CDI box could be the problem.

Over time of pulling that connector apart & pushing it back together on the CDI box, the male pin down inside the box can come loose from its connection, the workings inside the CDI & after that theres nothing to do but get another one.

I have when the ignition wasnt sparking, took & bent the wires around at the CDI box & then put a pull tye to hold them in place & the ignition would start sparking again.
Have also just simply sprayed WD40 all over the stator & flywheel & ignition would start back sparking.
I've heard of guys taking a C clamp & clamping it right in the middle of the CDI box, not real tight, & spark would come back, but I've never tryed that.
Neil

[DnB_racing]

Originally posted by C-LEIGH RACING
Check all the connectors in the wiring harness, that they are clean & fit tight sliding together.
The black wire with white stripe, is the main ignition wire & where it connects to the CDI box could be the problem.

Over time of pulling that connector apart & pushing it back together on the CDI box, the male pin down inside the box can come loose from its connection, the workings inside the CDI & after that theres nothing to do but get another one.

I have when the ignition wasnt sparking, took & bent the wires around at the CDI box & then put a pull tye to hold them in place & the ignition would start sparking again.
Have also just simply sprayed WD40 all over the stator & flywheel & ignition would start back sparking.
I've heard of guys taking a C clamp & clamping it right in the middle of the CDI box, not real tight, & spark would come back, but I've never tryed that.
Neil actually Neil the Black with white stripe wire needs to have no continuity to ground for there to be spark, the blk/white is the kill circuit ,

you can actually cut that wire right off at the cdi and it will still run (but dont do that) LOL

as Wilkin said the red/blk is the main ignition wire and power wire ..

but yes check that connection real good, make sure its dry and doesnt look brown or burnt, Ive had to actually tie the connector tight to the cdi with string to get home because a bad connection on the red wire,
try putting pressure and wiggle on the wires and check spark

[C-LEIGH RACING]

Is that just on the 86 model that the red wire is main ??.
Neil

[DnB_racing]

Originally posted by C-LEIGH RACING
Is that just on the 86 model that the red wire is main ??.
Neil no all years, there isn't much difference between the years, the key and swapped ipg wires are about the only difference,, the yellow is the auxiliary circuits and the red /blk is the ignition

on all years the blk/white is kill, even on the 400ex and the 450r the blk/wht is kill

Neil check the link for different years and race cuts http://www.exriders.com/vbb/showthread.php?s=&threadid=462117

[wilkin250r]

I'm not 100% certain (yet), but I think the red/black is pretty much shorted to the black/white wire inside CDI, they're almost the same thing. When the black/white wire is shorted to ground, this takes ALL the energy from the exciter coil and sends it to ground. No exciter coil energy, no spark.

[DnB_racing]

Originally posted by wilkin250r
I'm not 100% certain (yet), but I think the red/black is pretty much shorted to the black/white wire inside CDI, they're almost the same thing. When the black/white wire is shorted to ground, this takes ALL the energy from the exciter coil and sends it to ground. No exciter coil energy, no spark. yes!!! you just got me thinking about cdi failure,
I wonder if spark was lost thru the cdi,
if I was to take and put the output wire from the stator and cut the blk/wht at the cdi(removed from ground) and float the red, im not sure if you understand what im saying ..
but but basically remove both the blk /wht and the red/blk from cdi and tie the stator to the blk /wht ,,,it might bypass a open circuit in a bad cdi... I wish I had a bad one to try it..lol

Neil you probably could use the blk/wht as the ignition, but im not sure if I would want to keep it for the kill switch??

Wilkin do you think it would be bad for the stator, to have it tied to the kill without going though the resistance of the cdi first?

[C-LEIGH RACING]

DnB & Wilkins,
you guys remember Teamgeeks6 from Mac Dizzy, he was the 250R ignition guru did a lot of testing on the stators & CDI box & where I learned a lot about the system.
What he had listed in threads, from his testing, was that the black & white wire was main.

At Mac Dizzy, might could go back some years & pull up his old threads on the testing he did.
Even had one ignition system so hot, it would throw a spark a foot long gap.
Neil

[DnB_racing]

Originally posted by C-LEIGH RACING
DnB & Wilkins,
you guys remember Teamgeeks6 from Mac Dizzy, he was the 250R ignition guru did a lot of testing on the stators & CDI box & where I learned a lot about the system.
What he had listed in threads, from his testing, was that the black & white wire was main.

At Mac Dizzy, might could go back some years & pull up his old threads on the testing he did.
Even had one ignition system so hot, it would throw a spark a foot long gap.
Neil I will have to check his threads out..

From Honda's schematic I would have to say that their intended use of the blk/whit is to ground out the system, and use as a kill circuit

however I think your right about the blk/wht being a better terminal to hook up to , by doing this it does bypass some of the internal resistors in the cdi, and possibly removing some limits,

I hope wilkin has a old cdi to check this, if so some old cdi's could be salvaged

[wilkin250r]

Originally posted by DnB_racing
Wilkin do you think it would be bad for the stator, to have it tied to the kill without going though the resistance of the cdi first?

I don't think so. The problem with short circuits directly to ground is generally heat.

Power (which is the heat component) is voltage squared divided by resistance. When resistance gets really small, power goes through the roof.

However, like passing you finger through a flame, you're generally fine because it's not in the heat for long enough to do damage. If you short the exciter coil directly to ground, you have the potential to eventually overheat, but that's only if you continued to turn the engine and continue to pass that voltage to ground. However, after you hit the kill switch, you're generally not running the engine long enough to build up any significant amount of heat.

[spintly]

The Clymer manual is a great source to trouble shoot the individual ignition components. All you need is the book and a OHMs meter. The only thing the manual does not have a test for is the CDI box. I tested all my components when I had no spark and the CDI was the problem. All other compenents tested within spec. Hope this helps and good luck.