Revisiting old no start topic

Discussion specific to the 1989 - 1994 (E Series) KDX200 model sold in the USA
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90SDKDX
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Revisiting old no start topic

Post by 90SDKDX »



Above link is video of when bike stalled.

This past summer I posted on here regarding my 1990 KDX200 stalling out on me during my first and only ride on it during the summer. I bought a Beta 300RR so it got put off to the side. I'm going to start working on it again before the weather warms up so I want to revisit the topic.

Here is a basic summary of what I've checked and what happened.
Things I've checked:
Brand new reeds
Boot from carb to motor
Compression around 150
New spark plug
Have good spark and spark jumps factory gap spec (7mm if I remember correctly)
Carb is clean and new jet block gasket
New twin air filter
Tried my stock CDI and aftermarket Jaguar CDI
New Electrosport stator
Also tried adjusting timing marks on stator

Here's how the morning played out.
Went to start the bike in the garage and was not even trying. Unplugged the kill switch and she fired right up and revved out fine. I figured I had the problem solved.

Loaded up the bike and meet my dad for a ride (oh yeah it was Father's day). Started up after a few kicks, let her warm up, and started riding up the hill. On the way up we stopped a couple times and the bike never seemed to start hard.

Got a little ways further and then it stalled as seen in the video. We kicked and kicked and kicked and got nothing. Made sure I had gas in the carb and I did. So we towed it out far enough to where I could coast down the hill. As I was coasting down the hill I could pop the clutch and it would start, but it would blubber out any time I gave it throttle, just like in the video. My dad was behind me and said it was smoking fairly good when running.

Unloaded the bike at my house, tried starting it, and she fired up first kick and revved like nothing was wrong. Talk about being frustrated. Tried it the next day and several after that and never got it to fire again. Sometimes it kicks back hard and sometimes it kicks through fine. It will also backfire when its kicking back hard sometimes.

The only two conclusions I can come up with is either my tranny side crank seal went out or I have a spark timing issue. I'm leaning towards the timing. I've been meaning to do a leak down test, but don't have the kit and haven't had the time or money to buy one. There is no oil residue present on the stator side.

I wanted a second opinion again before I tear into it. I don't remember seeing the flywheel key sheered and the magneto spins in time with the crank when turning over by hand, but I may replace it anyways as a cheap check. Any opinions are appreciated.
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Re: Revisiting old no start topic

Post by bufftester »

The video sounds a lot like a fuel delivery issue. You didn't mention, but have you checked your vent tube for blockage and your petcock/tank for any much that could be fouling the screen. Probably a long shot, but low hanging fruit that doesn't cost you anything. A leakdown test should be done to check the condition of the motor. Even though compression looks good, a compression check doesn't give you an indication of the condition of your crank seals/bottom end. Double check the flywheel key as you already indicated, again, easy enough to do and doesn't cost anything. I had a KLX that did something similar and it turned out to be a combination of a couple things, one of which was bad grounds. Again, low hanging fruit to check/clean/verify that your grounds are good and corrosion free. The leak down really should be your next check before spending anymore money IMO.
90SDKDX
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Re: Revisiting old no start topic

Post by 90SDKDX »

bufftester wrote:The video sounds a lot like a fuel delivery issue. You didn't mention, but have you checked your vent tube for blockage and your petcock/tank for any much that could be fouling the screen. Probably a long shot, but low hanging fruit that doesn't cost you anything. A leakdown test should be done to check the condition of the motor. Even though compression looks good, a compression check doesn't give you an indication of the condition of your crank seals/bottom end. Double check the flywheel key as you already indicated, again, easy enough to do and doesn't cost anything. I had a KLX that did something similar and it turned out to be a combination of a couple things, one of which was bad grounds. Again, low hanging fruit to check/clean/verify that your grounds are good and corrosion free. The leak down really should be your next check before spending anymore money IMO.
Yes I have checked gas cap vent tube and petcock. I can pull the line off the carb and turn the petcock to either reserve or on and fuel flows. I hadn't really considered the ground issue since I always seem to have spark when I check, but maybe its losing that spark from the motion of me kicking. I have replaced the float needle as well and confirmed float height.
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Revisiting old no start topic

Post by SS109 »

Make sure the vent tubes that are on the carb are clear as well. Plug wire could be bad or coil dying when hot. Also, have you checked your silencer to make sure it isn't plugged up or something broken? I had a similar problem. Would run fine then just bog out. Chased everything but I noticed I had way more smoke than usual coming from my silencer so I decided to repack it to be safe. Turned out the main perforated tube broke and was bouncing around. Sometimes I got flow and sometimes it was choking it out. Anyway, just something to check.
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Revisiting old no start topic

Post by 90SDKDX »

SS109 wrote:Make sure the vent tubes that are on the carb are clear as well. Plug wire could be bad or coil dying when hot. Also, have you checked your silencer to make sure it isn't plugged up or something broken? I had a similar problem. Would run fine then just bog out. Chased everything but I noticed I had way more smoke than usual coming from my silencer so I decided to repack it to be safe. Turned out the main perforated tube broke and was bouncing around. Sometimes I got flow and sometimes it was choking it out. Anyway, just something to check.
To the best of my knowledge all my carb vent lines were clear when I last checked. As far the coil it doesn't want to start at all now, hot or cold, although I haven't tried starting it since July or so. The entire exhaust system was replaced with FMF system so I shouldn't have any bloackage anywhere. I suppose I could try removing the exhaust and see if it starts then.
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Revisiting old no start topic

Post by SS109 »

90SDKDX wrote:To the best of my knowledge all my carb vent lines were clear when I last checked. As far the coil it doesn't want to start at all now, hot or cold, although I haven't tried starting it since July or so. The entire exhaust system was replaced with FMF system so I shouldn't have any bloackage anywhere. I suppose I could try removing the exhaust and see if it starts then.
On the coil it could have been shorting as it got hot and then it finally shorted out completely. It happens. For clarity on the silencer, it was replaced before or after the problem?
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Revisiting old no start topic

Post by 90SDKDX »

SS109 wrote:
90SDKDX wrote:To the best of my knowledge all my carb vent lines were clear when I last checked. As far the coil it doesn't want to start at all now, hot or cold, although I haven't tried starting it since July or so. The entire exhaust system was replaced with FMF system so I shouldn't have any bloackage anywhere. I suppose I could try removing the exhaust and see if it starts then.
On the coil it could have been shorting as it got hot and then it finally shorted out completely. It happens. For clarity on the silencer, it was replaced before or after the problem?
I could see that with the coil, but I have spark. Is it possible to have spark outside the cylinder, but not inside? I replaced the silencer before the problem.
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Re: Revisiting old no start topic

Post by KDXGarage »

Yes, due to compression
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Re: Revisiting old no start topic

Post by 90SDKDX »

Jason wrote:Yes, due to compression
If this is the case, I would assume the problem is with the ignition coil? Maybe the secondary windings are only strong enough to spark outside the cylinder? My spark is jumping a 7mm gap though, if that matters.
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Re: Revisiting old no start topic

Post by 90SDKDX »

So an update to this topic. I went ahead and installed a new flywheel key and ensured it was keyed properly, just to eliminate that possibility for sure.

I really feel like this problem isn't mechanically related, just based on the fact that it started acting up out of no where and did happen to start one more time after the initial failure.

Again, I have spark and it jumps a 7mm gap, which is what the service manual calls for. Maybe the coil is not producing a strong enough spark when in the cylinder? I wouldn't think the bike would kick back though if it wasn't sparking at all.

I'm going to look at it again tomorrow after work. I'm really starting to lose my wits on this one. Have spark (so it appears), compression, and the plug is getting wet so I have fuel. Any thoughts are appreciated guys.
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Revisiting old no start topic

Post by 90SDKDX »

Okay so I worked on this quite a bit tonight and here's what I came up with. I rolled the bike out and decided I'd start by putting my original CDI and stator on ( had aftermarket units installed). Bolt it all back together, and two kicks later it starts! Now I let the bike run for a while to see what happens and it sort of randomly shuts off. Kick it over, it fires, and dies almost as quickly. So then I pull my carb again to look for debris. Sure enough there are pieces of something floating around in there. So I clean all that out, take my fuel tank apart, and clean it all out. Put it back together and the bike is running great now. Take it for a couple of laps around the shop and it starts acting up again, very similar to the video, except it was sometimes cutting in and out(jerking motion from the bike). Take it back inside and shake my head in confusion. So now I start testing my ignition coil as it's the only part of the ignition system I haven't thoroughly checked, as it has spark. Primary ohmed fine, and secondary ohmed fine with spark plug cap removed. I then looked a bit closer at my plug cap and see that some of the metal seems to be missing / broken. I now figure I found my problem, so I put a new spark plug cap on and ride it again. Unfortunately it acted up just as bad as before. Now this all took place over the course of a few hours, so there is a good amount of time between runs(i.e. parts heating up and cooling down) . I pull it back in one last time, and again check my ignition coil resistance. Primary has continuity, and ohms close to spec, however the secondary now seems to read Open, regardless of whether I have the plug cap on or not. This leads me to believe this is my problem, even though I still have spark. My thought is the ignition coil may be cutting out intermittently. To me it's the only thing left to check. I plan on ordering one on Ebay and praying that fixes it. If you have any thoughts, feel free to share.
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Re: Revisiting old no start topic

Post by KDXGarage »

It sounds like you are headed in the right direction.
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Re: Revisiting old no start topic

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Jason wrote:It sounds like you are headed in the right direction.
Thanks Jason. Will let you know once I get one installed if it fixes it.
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Re: Revisiting old no start topic

Post by 90SDKDX »

Hello everyone. I've got an update on this bike. So a couple weeks ago I got the new ignition coil, installed it, and still running poorly. So long story short my bike now seems to running very rich when on the pipe. I've went from a 152 main down to a 150( or 148) and it seems to be getting better, in the sense that its taking more full throttle before it starts stalling out. I also raised my needle one position. The thing I don't understand is that it was running well and showing a darker brown plug before this happened. Perhaps I just never ran it wide open enough before to get it to stall. I'm currently looking for a replacement intake manifold boot as mine is getting near replacement, and once I have that I'll finish dialing in the jetting and hope that was the issue all along.
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