Need HELP with intermittent ignition problem...

[jazzjourneyman]

Hello from Dennis in Ohio...

I started having problems with my used 98 KDX 220 the day after I bought it... arrrgh. It began cutting out when riding, then wouldn't start. I removed and cleaned the carb, bought a new plug, and it started right up today. After about two minutes, it died just as if I'd hit the kill switch and would not restart. After a few minutes, it started right up again, then - died again. I am suspecting the coil, or the ignition wire from the coil to the plug. Are either of these prone to malfunctioning after warming up a bit when nearing failure anyway? Is the ignition wire itself replaceable if the coil is ok? I did remove the boot from the end of the ignition wire and at first had no spark to engine case. I pushed this ignition wire up toward the coil, then had strong spark arcing about quarter inch. After putting it back together, it again ran for a few minutes... then died.

I have a downloaded manual for a KDX 200. Is the coil testing procedure the same for a 220? Can I perform these resistance measurement tests with the coil on the bike, or does it have to be removed?

I am frustrated as hell, and would greatly appreciate any help or advice.

Dennis :bang:

 

[nmilne]

Check wiring ... a wire that has worn through its insulator and is arcing on the frame will cause your bike to cut out intermittently. A problem I had was with one of the wires breaking near the base of the connector that went into the cdi, which caused the bike to cut out intermittently. Fixed with a tek screw :)

 

[jazzjourneyman]

Hello nmilne...

Thanks for the reply! Yes.. I will check wiring more closely. Yesterday, I had the bike running and moved/shook/pulled [gently] every wire I could find trying to get it to quit, and thereby find a short, or a poorly grounded wire. No luck.

Because the bike runs longest [about 5 minutes] when started from a dead cold start - then runs for less than a minute after cooling down a bit but still warm, I am thinking this problem is likely heat related. Wires that are close to heat sources could move just enough to cause a short I suppose. Hmmmm....

My instincts tell me this is a wiring short as you suggested - or a grounding problem. What I am trying to avoid is blindly replacing stator, CDI and ignition coil if those components are not the cause of the problem. So after checking wiring, I need to find ways to check these components.

Testing the ignition coil looks pretty straightforward. I'll do that. Can anyone tell me if the ignition wire from coil to plug can be replaced if that's the problem in an otherwise working coil. Plus, can the ignition coil measurements be taken while mounted in place, or must it be removed first?

I'd like to find a way to measure the output of the stator. With the plug out and the bike leaned on kickstand, I can turn the engine over readily with a hand on rear wheel. What output should I expect from the stator, and where can I measure this voltage?

Cheers...

DT :think:

 

[dirt bike dave]

When my stator went bad on my old '84, it acted the same way. Temperature sensitive, bike would shut down and not restart when it got hot. Ran fine when cold. It just kept getting worse (less time before shut down, harder to restart).

It was difficult to diagnose, and the stator was within spec when tested cold with an ohmmeter.

Rewinding the stator cured the problem.

 

[jazzjourneyman]

Hi Dave...

How did you test the stator? I'd assume that if this is the problem, it would read within spec when cold, and if measured immediately after warming up to shut down point, would read differently.

Thanks for your help.

DT

 

[liven07]

This sounds like a fuel problem the way it runs then dies. Next time that thing dies shut your fuel off at the tank and pull your carb with out tipping it, then holding it straight up take the float bowl off and see if it is full. Most of the time electric parts just die and thats it for them (not saying they cant work a little and be going out because it does happen just not likely) but you were talking about not seeing spark, on my bike you would swear the bike did not get no spark unless you new it ran, you cant see any spark unless you have the plug in the right spot. I would be willing to bet your carb is slowly filling up to run for a while then dies.

 

[dirt bike dave]

Hi Dave...

How did you test the stator? I'd assume that if this is the problem, it would read within spec when cold, and if measured immediately after warming up to shut down point, would read differently.

Thanks for your help.

DT

There was a range specified in the old '84 owner's manual for resistance across the stator. Sorry - can't remember what the figure was in ohms. I remember testing the resistance cold after I popped the flywheel off, just before I sent it in to be rewound, and it was in spec. I can't remember if it is something you can test with the flywheel on.

Luckily for me, the stator rewind was the first thing I threw money at (cheaper than a CDI).

It was an informed guess because I'd heard of it happening on the mid '80's KDXs (I was the original owner of my '84; the stator went bad about 1987). There was a guy in Colorado who used to advertise in Cycle News, and I sent it to him. He's no longer around, but there are other places like Ricky Stator.

It does seem rare on the '89+, but your symptoms sound exactly like what mine did.

First time it happened, the bike stalled on a trail ride. Let it cool a few minutes - everything was fine for the rest of the day. Next time on the bike, I was at a MX track/small park. Died after a 30 minutes or so of running. Took at least 10 minutes to restart. By the time I got back to the truck, it was dieing again. Let it cool 30 minutes or so, then the bike ran about 20 minutes before it died. Took a long time to restart. Brought the bike home, knowing I had a problem.

Started looking for the problem. Would do lots of testing and tuning. Bike would start fine when cold, run 15 minutes before stalling. then 10 . Then 5. Harder to start each time. By the time I sent the stator off to rewind, it would barely start cold, and would run less than 5 minutes and have to cool down completely before it would restart.

It was 100% cured with a rewound stator installed.

 

[jazzjourneyman]

Hi Dave...

Yes, that sure sounds like what my bike is doing. Do you know whether it is possible to measure the output of the stator [AC voltage?] with bike cold, plug removed and back wheel turned by hand while in gear to have engine spin for a few seconds. I'm thinking that if I confirm I have spark, then run this test and find voltage - then warm up till engine quits - then quickly run test again, I'll probably find no voltage so can confirm stator problem. Does that sound logical?

 

[dirt bike dave]

Sounds logical to me.

But another variable is vibration. Going to be hard to simulate that during testing.

Honestly, after the way mine behaved, it would not surprise me if it passed the resistance/ohm test both hot and cold, but it still turned out to be the stator.

Overall, it was the most frustrating thing to diagnose I've ever had.

Up until my bike fired up with the rewound stator, I was not sure I was on the right track, despite many hours working on it and thinking about it.

 

[jazzjourneyman]

Thanks Dave... I will do a bit more testing and let you know what I find out. Your advice and suggestions are greatly appreciated!

DT

 

[reepicheep]

Where in Ohio are you? Cincy / Dayton area?

 

[jazzjourneyman]

yes... near Cedarville/Yellow Springs

 

[jazzjourneyman]

What about you?

 

[podfish]

I have the same story as Dave. I don't think that tests with a volt/ohmmeter will show the problem, but stators are pretty cheap (~$40 from RickyStator) and he's great to do business with.

 

[reepicheep]

I'm in Lebanon, near Cincinnati, about 2 miles from Kings Island... I'm new to the KDX, but I am rebuilding mine from the ground up and it's going pretty well, and my previous owners made sure there is nothing about a KDX that I don't have experience fixing :(.

If you were closer, I would drop by with a meter and we could do some quick tests, but Yellow Springs is a bit of a haul...

My stator problem was easier to diagnose... said previous owner let a leaking crank seal go, which contaminated the stator, and dissolved the insulation on the windings on one of the coils.

I can slap a meter on mine tonight (I got a new stator on ebay) and see what the resistance is. A stator is simply a long single strand of copper wire that is wound in a specific pattern. When you move a permanent magnet through this field, it induces (a) a resistance force on the magnet and (b) a current through the wire.

The stator can fail in a couple of different ways.

It can fail "open" where that long continuous piece of wire breaks somewhere (either in the coil or more likely at a connector). That is easy to check, put your meter on Ohms and put each lead into each of the stator wire connector openings (use a small wire to get in there if your leads are too big) and measure the resistance. If it's infinity (basically what you get when you don't have the leads touching anything but air), the wire is broken somewhere, and the stator won't work.

The second failure mode is trickier (and in my experience, more common). The insulation on the stator coils fails, and two coils short out against each other. To test this one, you again measure resistance, but you are hunting ghosts at this point. A cheap digital multi meter is lucky to read accurately below one ohm, and the "normal" resistance of the long piece of wire used for the stator is probably something like .4 ohms or less. So you are trying to spot a change from .4 ohms to .2 ohms or something, depending on where the coils have shorted. A good meter can do it (I still have my trusty Fluke 77 I bought with my first co-op pay check 20 some years ago), but the basic Harbor Freight $9 meter won't.

The third failure mode (a minor variation of the second) is when the insulation fails, but the stator shorts to the cases or to a bolt instead of just to itself. That is easy to test as well, just measure Ohms between each stator pin and the engine case. Both should be infinity.

Finally, you can just look to see if the stator is doing what it is supposed to do, at least if you can get the motor running. Fire it up, pop off that wire, and measure the AC voltage coming out of it. Your meter (unless you spent a boatload of money on it) won't read it that accurately because it is not at 60 HZ, but it'll be good enough for the task at hand, and you should see something like 20 volts off idle, and maybe something like 30-60 volts with the revs up (I'm guessing at those voltages, the manual no doubt has the real ones).

I'll try and remember to slap a meter across my stator terminals tonight (both my good one, and my known bad one) and I'll post what I see...

 

[liven07]

That really sounds like your carbs float bowl is filling very slowly and when it sits it slowly fills up then runs good till the fuel is gone and like when it starts 2 min later then dies it just got enough fuel to start the die. I don't know if you tested that carb or not but would strongly suggest it before you buy a stater. It don't cost a dime to pull the float bowl off or the plug in the bottom of it and see how well the fuel is coming out.

 

[jazzjourneyman]

Problem SOLVED!

Thanks to everyone for the advice - especially reepicheep for the detailed explanation. As I mentioned at the outset, I purchased this bike and started having problems the following day. I called the previous owner to see if he'd had any stator problems, and he indicated he had the stator [whole unit] replaced two months prior, and gave me number of mechanic. I learned that a Moose Engineering stator was installed, and it had a one year warranty. Electrosport is the manufacturer, and they agreed to send me a new one. Cool! Except they sent the wrong last week, and the correct one this week. I installed it today - and it started right up. Yeeha!

FYI I learned along the way that a good source coil [generates voltage going to CDI] will pump out about 20 volts AC when bike is kicked - measured between red/white and black [ground]. My original stator generated only 3.6v AC, then died completely. In any event, now I know how to check a stator other than the static ohms test.

BUT.....

Today, when I tried to start the bike, I could not find neutral... finally did, and bike would not shift out of first.... then got stuck in second... then finally acted if it was terminally in neutral - had to push it back from the woods... arrrrrgh [but at least it was running great :P

I've read that KDX engines are bulletproof - and I've read that you shouldn't buy a KDX if you don't like working on them. I am leaning toward the latter. And I know... buy used and you get what you pay for... but damn... I want to ride this thing!!!!

DT

 

[reepicheep]

Thanks for posting the expected measurements... that'll be helpful.

Your don't have a transmission or crank seal leaking, do you? Is the transmission fluid level still OK when the transmission gets fussy?

 

[dirt bike dave]

On the shifting problem, the two times I had a KDX act up shifting were the following problems:

1) Shift shaft return spring popped out of place. This is under the right side cover (brake lever side - the shift shaft extends all the way through the cases). I had to shim it with a washer to keep it in place on my old '84.

2) Used a gear oil in the tranny - was too thick when the bike got too cold sitting out overnight in freezing weather.

Sounds like your KDX was very well used when you got it - they normally are very reliable for a dirt bike.

 

[jazzjourneyman]

Thanks Dave...

I am hoping the trouble is in the area you described. I copied the pages out of the KDX 200 manual and will pop the side cover to inspect.

Cheers...

DT