ELECTRONIC GURU NEEDED - STATOR QUESTION

[GG]

My friend is at his wit's end. His 1994 Yamaha XT 225 has very weak spark. It uses a "pulser coil" to generate voltage, that passes through the cdi and goes to the high voltage coil. Another "timing coil" send the signal for the spark at the proper time. The measurements of the coils all check out fine - they are all within the correct numbers according to the Manual. But the spark is so weak the bike won't start.

This condition was somewhat gradual. First it wouldn't start with the electric start. Then hard starting, and then finally died.

We suspect the stator (which has the pulser coil integrated). But we are puzzled because the resistance numbers are correct.

We understand that the cdi doesn't affect the amount of voltage, but rather "coordinates" the operations. Or are we wrong.

ANY HELP WOULD BE APPRECIATED. The guys on ThumperTalk (the forum for xt's, etc) couldn't help us. So I came to my favorite forum.

I told my friend he should just get a Superhawk with points and condenser and he'd be done suffering...

GG

[teazer]

The pulser is also known as the Trigger coil. It sends the timing pulse to trigger the ignition.

There is usually a single charge coil on the stator that sends the "power" that the CDI turns into a spark.

Normally I'd think that the problem is a battery on its last legs but that bike doesn't use the battery that way.

It could be a bad plug, bad plug cap or bad connections through the kill switch or clutch switch and I'd start with that easy stuff. All the connections should be checked and cleaned

CDI's usually don't fail that way but an easy way to check is to borrow a CDI and swap it out.

[GG]

Hi Teazer,

Thanks for the reply. I didn't put in all the info - we have already cleaned and checked all the points you mentioned. We've been over every part of the electrical system a hundred times (well, maybe not a hundred, but...!) The charge coil on the stator was black - like it was burned out - and we had it re-wound. But the problem is the same - very weak spark. Now we are not sure if the re-winding job was bad, of it is something else.

The xt225 doesn't use the battery for spark, but the battery is good, and we've even jumped the bike to see if that helped. No change. We've tried various spark plugs, changed the high-voltage coil, checked the cap (quite new), cleaned the kill switch and checked the ignition switch and clutch switch. All checks out good. Essentially we are at our wit's end!

The charging coil gives the right reading. What we'd like to know is if it is possible to give the correct ohms but still be deficient in power. And if the cdi can affect "weak" spark. No one will lend us a cdi - they are too costly here in Costa Rica! No one wants to risk it.

Thanks again. We'll figure something out eventually, but this one has been a dilly!

GG

[brewsky]

No guru here, just throwing a couple things out there...

air gap in spec?

ground connection corroded?

any chance someone heated the flywheel to aid removal...and whacked on it, weakening magnets?
(although this doesn't fit the gradually increasing problem symptom)

what voltage do you get at the coil?