Coil Rewinding ???

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#1
Re. Help needed PLEASE.

Well i got the coil back last night. And to everyone who wanted to know from my previous thread, it did work to get the bike sparking like a brand new bike, & the spark jumps a good 20mm. BUT now the bike is firing completely out of order and still does the exact same thing as it done before I had the coil done

Guess i should have just left it alone.

Now comes my new question please.

What could cause the bike to fire out of order, And i might ad that the guys from the shop are more confused than I am,they say it could be the CDI.
But they cant test it because according to them it is unique to that specific model (91) . Can i get a CDI from a another model that will work on my bike.

I can get one now from a +- 89 model.
 

dirt bike dave

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#2
Perhaps the woodruff key that locates the flywheel on the crankshaft has sheared, allowing the flywheel and its magnets to be out of position. This wil cause the spark to come at the wrong time.
 

Canadian Dave

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#3
Could you give us a list of what's been checked to date so we don't have you running around in circles?

Have a look at your CDI and tell us what part number it is. You should be able to test it and at least see if there is a dead short some where. Do you have a multi meter?

Do you have a friend with a 89 to 94 KDX200 you could swap CDIs with and see if the problem follows the part or not?
 

dhoward

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#4
What Dave and Dave said. First check the key in the crank.
Second, the CDI is essentially an electronic on-off switch, so if you know which lead is which, you should be able to swap one in from nearly any year.
Did you check to make sure the timing marks on the stator plate are lined up correctly?
You didn't accidentally swap the position of the lighting and trigger coils?
Where in the stroke does the plug fire?
 
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#5
CDIs often are designed to fire twice per cycle, once at the top where they ignite the mixture & once harmlessly at the bottom, which helps keep the plug clean. Keep this in mind so it doesn’t catch you out. (Not all systems do this & not sure for KDX).

As I originally suggested in a past thread a sheared woodruff key is possible. Basically the flywheel magnet that passes by the pulsar coil (& therefore the position of the coil) determines the position that the SCR (in the CDI) is tapped on the shoulder & opens the gate to discharge the capacitor through the coil.

Yeah I’d look real hard at the backing plate & your wiring to see the right coils are wired correctly to the right CDI wires. If the pulsar (not the charge) coil is wound incorrectly it may affect the timing slightly but this sounds like way more than that. You never said which coil was rewound, though you make it sound like it had a weak spark which indicates the charge coil (maybe lo speed one depending on ignition type).
 
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#6
Here is the list of what has been checked.

Woodruff key (replaced before I wrote the thread)
compression (new piston , rings , powervalves)
spark plug (replaced)
plug lead ( fine)
Arrestor cap (replaced)
Charge coil (rewound)
CDI (being checked )
Carb (Float level etc.

I just finished speaking to the guy from the bike shop. He said that they have found the problem on the cdi. It seems that there is two resistors that has blown , and he can only make the value out on the one resistor. Doe's anyone know the values of these resitors.
Any help would be greatly appreciated, THANK YOU
 
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#7
Remember what I said about coils and misdiagnosing them as failures? (sorry..just had to say that!)

I'd replace the spark unit before I'd have someone replacing parts in one. Aren't they expoxied/potted for structural integrity anyway? Getting a piece out and correctly resoldering the replacement in a 'sealed' unit is likely going to cause more problems than it fixes.

I'll bet'cha CDave can tell you make model and year of every KDX made that will fit on your bike.
 

dhoward

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#8
I really didn't think you could open up a CDI for the reason Canyncarvr mentioned. Measuring resistance through the leads WILL give an indication of the condition of the junctions in the SCR ( shorted or open). Prolly have to replace it as a unit.
 

Canadian Dave

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#9
I want to double check what you're saying. It sounds like your dealer is telling you that 2 out of the 3 connections he tested are bad? Does that sound right? If memory serves me right he should be checking a total of about 20 combinations, some of which should give a short. I'm not trying to put down your dealer here just want you to be careful before shelling out a bunch more money on parts that aren't damaged. He should have easily been able to check your coil for you and confirmed it was in good operating condition so I'm erroring on the side of caution.

Does anyone have the CDI Unit Resistance table for an 89 to 94 KDX200 kicking around? Its in the shop manual.

Do you know anyone else with an 89 to 94 KDX200 you could swap CDIs with and see if the problem follows the part? A CDI isn't cheap so you want to be sure it's the problem before you shell out the cash!

David
 
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agitt73

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#10
i blew the source coil on my it 250 a couple of months ago
got a new coil and it would only go to 1/4 throttle with out
missing really bad so i put on a timing light and the ignition
was not advancing all the way so i replaced the pulsating coil
and cdi still the same
so one day i was tinkering and never put the silencer back on
and tooker for a spin it ran like new without the silencer come
to find out when i laid the bike on its side the spark arrester
came loose and was misaligned and pluging the exhaust
$300 bucks later it was A WASTE OF MONEY:think
 
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#11
Well it seems to be getting worse by the day. I only know guys with newer model kdx's.

He says now that he can't get the right value resistor for the CDI. But he is taking it to someone else who knows more about CDI's than he doe's. (I don't even know why he even touched it if he doesnt know exactly what he was doing.) But so the lessons of life are learnt:(

Seems like this will be turning into a very expensive affair.

I Will know by tomorrow if this new guy knows what he is doing.

Thank you for the help so far, and more help be greatly appreciated.

Rudy
 
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#12
imo.....

Take your troubles someplace else. The guy with the, 'I could replace them if I could just read their values,' idea is doing you no favors.

Resistors don't 'blow out'. Replacing them without fixing what CAUSED the problem is a waste of time.

Maybe the 'guy that knows more...' than he does can straighten it out. Still...I think you'd be better off (the diagnosis being correct) to buy a replacement unit than to 'fix' yours. After it's FIXED, it's going to need to be REPAIRED anyway.

Sorry 'bout that.
 
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#13
After a great mistake, I got my bike back last night :) Seems that the other guy knew a bit more about the CDI unit on my KDX. I have also decided to get rid of the bike at the end of the month, (It is time to upgrade to a newer model KDX) And I am also affraid the bike is going to leave me stranded one of these days. We do some harescrambles and it is of course not the place to be stranded in.

Just a word of thanks to everyone who gave their oppinion. I will keep everyone posted as to hoe long this CDI will last