Strange Electrical Gremlin (High RPM)

Got questions? We got answers....
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

Took the 'ol 220 out this weekend to blow the cobwebs out of it, I think I've been so busy riding motocross this year that I only put an hour or so on the KDX. I've got a very strange electrical issue that I'm chasing now. At high(er) RPM, it will cough and miss and pretty much die out. I have narrowed it down to an electrical issue, because it is completely RPM dependent, and has nothing to do with throttle position, or engine load. I can barely crack the throttle in neutral, and as the RPMs climb, at a certain point it will lose spark intermittently. If I go wide open throttle, it will almost kill the engine until the RPM's fall back down. I've been chasing this issue for a couple days, here is what I have tried so far, hoping someone here might have seen this before and have some suggestions. Engine is now hard to start compared to what it used to be, however seems to idle fine and rides fine as long as I lug it and stay at low RPM.

- It SEEMS to be more apparent once the engine is warm, vs when it's cold, however I make a point not to rev it too high when it's cold anyways.
- New spark plug, spark seems awfully weak when I test it. Gapped correctly.
- Still have my upgraded lighting stator, headlight functions as normal.
- Ignition timing set to default middle mark.
- Flywheel is on correctly, woodruff key is fine. (See my previous thread on when it grenaded. Bike has previously run fine since that whole debacle.)
- Kill switch functions properly, tried disconnecting it in case of intermittent fault, no change to my problem.
- All electrical connectors checked, not corroded, dielectric grease is doing it's job.
- Removed spark plug cap, exposed fresh wire, re-installed. No change.
- Tested ignition stator, resistance as per shop manual.

Image
'00 KDX 220R
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

Update:

Tested the CDI module as per the shop manual, using a multimeter and testing across the various wires as indicated in the table in the service manual. On about 4 of the 6 wire pairs that I'm supposed to have a resistance reading on, they showed as an open circuit. Seems very strange that a CDI could fail like that, and if it did, that the engine would run at all? I'm going to have a go at testing the coil itself tomorrow, and I'll have one more look at the stator plate connections and stuff.

If it is the CDI, are those cheap (I assume chinesium?) Ones on eBay any good as a replacement? I didn't think the KDX CDI's were very prone to failure, or maybe that's the ignition coil I'm thinking about.
'00 KDX 220R
John_S
Gold Member
Gold Member
Posts: 875
Joined: 06:59 am Jan 27 2017
Country: US
Location: Florida

Re: Strange Electrical Gremlin (High RPM)

Post by John_S »

I remember a post from a while back (I think it was Eric R) that bought a CDI off of Amazon for $28 and it fixed the issue he was having. When I checked them there was a slight difference in part numbers from 200 to 220. I meant to order one just to have and then got sidetracked.
User avatar
SS109
KDXRider.net
KDXRider.net
Posts: 5770
Joined: 05:11 am Aug 23 2009
Country: USA
Location: Tucson, AZ, USA
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by SS109 »

IIRC, you can't test the CDI with a standard multimeter. You have to have that special Kawasaki tester or the readings will be off and meaningless. I think KDXgarage and several others can shed some light on that. That CDI that EricR found on Amazon for the 200 is this one:



... and here is the one listed for the 220:



Honestly, $42 is cheap for a CDI replacement. I've been meaning to pick up one for my bike just to have as a backup and test part for when a situation like yours might come up.

With all that said, I would be leaning towards the coil which is another cheap replacement part. They tend to fail more often than CDI boxes but who knows. I would probably just buy both, figure out which it is, and keep the other part as a spare. The good thing is at least we have some fairly cheap replacement parts available for our old KDX's!
Youtube Channel: WildAzzRacing
AZ State Parks & Trails OHV Ambassador - Trail Riders of Southern AZ
Current KDX: '98 KDX220
Old KDX: '90 KDX200 -White/Blue
'11 GasGas EC250R
User avatar
KDXGarage
KDXRider.net
KDXRider.net
Posts: 14047
Joined: 06:45 am Nov 01 2004
Country: United States of America
Location: AL, USA
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by KDXGarage »

Can you borrow a coil from someone?
Thank you for participating on kdxrider.net. :bravo:
To post pictures from a device: viewtopic.php?f=88&t=24128
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

KDXGarage wrote: 08:37 am Nov 29 2021 Can you borrow a coil from someone?
I've got a spare two wire off my KX125, but I'll just go ahead and replace the coil and CDI they're cheap. The only other thing that would leave is the source coil really.
'00 KDX 220R
User avatar
KDXGarage
KDXRider.net
KDXRider.net
Posts: 14047
Joined: 06:45 am Nov 01 2004
Country: United States of America
Location: AL, USA
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by KDXGarage »

I'll bet one dollar on coil of some sort due to high heat making it worse. From what I have read over the years, a CDI usually works or does not work.
Thank you for participating on kdxrider.net. :bravo:
To post pictures from a device: viewtopic.php?f=88&t=24128
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

KDXGarage wrote: 09:45 am Nov 29 2021 I'll bet one dollar on coil of some sort due to high heat making it worse. From what I have read over the years, a CDI usually works or does not work.
I haven’t tested the coil yet, it should be easy enough I believe the manual lists resistance values for both the primary and secondary. About to wash the filth off from yesterday’s ride and then I’ll get after it.
'00 KDX 220R
User avatar
ericr
Gold Member
Gold Member
Posts: 246
Joined: 06:57 pm Nov 06 2017
Country: USA
Location: Gig Harbor, WA

Re: Strange Electrical Gremlin (High RPM)

Post by ericr »

I had very similar symptoms that a new CDI completely cleared up.
'02 KDX 200, '02 KDX 220 - My restoration thread
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

Is there someone with an A or H series with a known good ignition stator, who could take a resistance reading for me? Need the value across the WHT/RED wire and the BLK wire, in ohms please. Shop manual states the minimum resistance should be 250 ohms, I am just slightly below that. Wondering what a known good stator winding checks out at. The service manual states "if the resistance is much less than this value, the coil must be replaced."

Well, that's open to interpretation isn't it? How much is "much less?"

Primary winding in the ignition coil tested no good, will update with pics tomorrow.

Image
Last edited by Slick_Nick on 09:56 am Nov 30 2021, edited 1 time in total.
'00 KDX 220R
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

Tested the ignition coil, looks like the primary winding is out of spec. Luckily, coils are cheap to replace! I'll start with a coil, and maybe a source coil / stator depending on what results I can get from you guys on here.

Primary spec: 0.16-0.24 Ohms ACTUAL 0.40

Secondary spec: 5.0-7.6 kOhms ACTUAL 5.83

Image
Image
'00 KDX 220R
User avatar
Molly's 70
Platinum Member
Platinum Member
Posts: 563
Joined: 04:29 pm Jun 18 2017
Country: USA
Location: Wichita, Kansas USA

Re: Strange Electrical Gremlin (High RPM)

Post by Molly's 70 »

Oh Slick one. My ignition stator reads 312. Bike is handy if you need more.
If you lend someone $20, and never see that person again, it was probably worth it.
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

Molly's 70 wrote: 02:20 pm Nov 30 2021 Oh Slick one. My ignition stator reads 312. Bike is handy if you need more.
Thanks much! As I suspected, my stator is either on the way out, or will be soon. While it's close to spec, I'm sure its not doing my ignition system any favours. I'll look for a replacement, they seem to be only $70 or so on eBay or Ricky Stator.

Edit: What the hell am I thinking? I've done a couple stator rewinds before! surely an exciter coil is just finer wire, with more wraps around it! Worth a shot!
'00 KDX 220R
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

My stock exciter coil was just barely outside of the factory tolerance, and since I wanted to rewind my lighting coil anyways, I figured it was as good a time as any to try my hand at the exciter coil too. I couldn't find any information on the wire used for the stock coil, but I figured I would go with the finest I could procure, so if anything it would have a higher output than stock. I'd rather have too much spark, than not enough, however one must be careful not to go too far overboard.

I have never done this rewind before. This is an experiment for me. I took some "educated guesses" on wire gauge, winding procedure, etc, but the only way to know if this will work will be to try it out. I have a new ignition coil coming today.

In theory, a higher voltage stator will produce a better, stronger spark at lower RPM, making the bike easier to start. However, there are a few considerations:

- I couldn't find any specs on the stock CDI, in terms of what it can handle in input voltage. 400v? 700v? I don't even know what the stock winding outputs at higher RPM. A winding that's "too good" could fry the stock CDI at higher RPM.

- More windings of a thinner wire will mean more resistance when measured. This will need to be noted, as the factory spec is only good for a factory winding. If I ever want to diagnose my winding in the future, I'll need to refer to my "known good" spec of when I just rewound it.

Onto the process:

First, the stock stator must be disassembled. This is a colossal pain in the ass. There are a LOT of wires encapsulated in a hard epoxy, with pesky bits of silicone over the terminals.

Image

With the wire removed, I cleaned up the plates in the bead blast cabinet. This was a bad idea. The stock plastic "cage" basically disintegrated. It's not hard plastic, or at least not anymore after 22 years of service. It was almost like a dried sort of play-doh consistency. It flaked off easily with my fingernail. Looking online, most rewinds are done by wrapping the core and sides with cardboard, I didn't like this route, so I made a small repair to the one side plate with JB, and wrapped the core with thin tape. All we need is a barrier from abrasion around the core.

Image

I quickly welded a tiny fixture to hold the stator in my little lathe, and got to winding. I used 36 gauge magnet wire. Because this is a single phase, AC stator, winding direction does not matter. ***Yes it does on the KDX specifically! See page 2!***

Image
Image

I lost count of the wraps, but this was maybe 100-150 layers. Getting there!

Image

All finished! I tried to stay within the same dimensions as factory. Getting this far took me about 90 minutes. Twice, I had the wire break on me, and had to completely unwind and restart. This wire is about as thick as a human hair, you need just enough tension to keep it taught, but not so much that you snap it. It's impossible to count, but if I had to guess I'd say this was anywhere from 300-400 wraps of wire. Used about half of a 1/4 lb spool. Once the winding was finished, both ends were quadrupled up and twisted for strength, and some cloth tape was used to secure everything for now.

Image
Image
Last edited by Slick_Nick on 04:53 pm Dec 08 2021, edited 1 time in total.
'00 KDX 220R
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

Before we get to the epoxy phase, lets make sure our work is sound. I stripped the enamel off the ends to be soldered, and cut them to length, then using a flux paste I soldered them onto the terminals.

The stock coil has a resistance of 250-320 ohms. Since I used a finer wire, and squeezed in more wraps, we are expecting a higher resistance value. I was a little surprised however, to see 769 ohms on the meter. I'm sure I don't have an open, or it would read as such on the meter, and I used two different testers and got the same result. I think it's just THAT much more skookum than stock. Will it blow the CDI? One way to find out!

Image

Satisfied that my winding wasn't shorted, I coated it with an electronic silicone conformal coating. Basically like a clear, brush on epoxy. Dries hard and keeps everything in place. The coil is finished and ready to be reinstalled on the stator plate. Also a few pics of the lighting coil I re-did with 18AWG wire.

Image
Image
Image

It might not look like much, but hopefully it's funcional! I'm awaiting the arrival of my new ignition coil today (remember that's what tested bad) so I can get to testing this stator out. It may prove to be an awesome upgrade, or I may have gone too far and it sends my CDI into orbit with the first kick. Only one way to find out! Stay tuned for further.
'00 KDX 220R
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

Got the stators mounted back up to the plate, routed the wire harness in it's factory location, set the ignition timing to the default center mark, and installed the flywheel. Still waiting on my new ignition coil, but just by kicking the engine over, I was able to see 68 volts AC from the new rewound stator.

Image
Image
Image
'00 KDX 220R
User avatar
KDXGarage
KDXRider.net
KDXRider.net
Posts: 14047
Joined: 06:45 am Nov 01 2004
Country: United States of America
Location: AL, USA
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by KDXGarage »

VERY NICE! Curious to hear how it goes.
Thank you for participating on kdxrider.net. :bravo:
To post pictures from a device: viewtopic.php?f=88&t=24128
User avatar
SS109
KDXRider.net
KDXRider.net
Posts: 5770
Joined: 05:11 am Aug 23 2009
Country: USA
Location: Tucson, AZ, USA
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by SS109 »

Man, you always impress me when you get going on a project! Please keep us posted!
Youtube Channel: WildAzzRacing
AZ State Parks & Trails OHV Ambassador - Trail Riders of Southern AZ
Current KDX: '98 KDX220
Old KDX: '90 KDX200 -White/Blue
'11 GasGas EC250R
User avatar
MoonStomper
Gold Member
Gold Member
Posts: 560
Joined: 02:05 pm Jun 02 2020
Country: USA
Location: Blacksburg, Virginia
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by MoonStomper »

After carefully reading the above detailed description of work, I am reminded of my wholly inadequate state education that was not helped by my complete lack of aptitude for all things mathematical and electrical. Still fun to read about. When mine goes KAPUT, it will arrive on your doorstep Sir!
~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~
Let the good times ROLL!!!!!!!!!!!!!!!!
‘99 KDX 220 / '03 KDX 200 - @%@ '18 Trek Slash 8 @%@ ‘22 Rieju MR300 Racing

BLACKSBURG, VIRGINIA USA
User avatar
Slick_Nick
Supporting Member
Posts: 1675
Joined: 10:06 pm Oct 22 2009
Country: Canada
Location: Calgary, Alberta
Contact:

Re: Strange Electrical Gremlin (High RPM)

Post by Slick_Nick »

Got the new coil installed, just one I picked up from the gettin spot. Kicked it over with the spark plug out and saw a super strong, nice bright blue spark. Much better than the faint hint of a spark I had before!

I’ll fire it up tomorrow. There’s a bit of snow here so I won’t be able to take it for a ride, but I’ll take it through the rpm range as best I can on the stand to make sure everything works.
'00 KDX 220R
Post Reply