I've got a 2009 KLX250S (EFI) with 67000km on the odometer.
I service the bike myself and generally take good care of it. Oil changes every 2000-3000km. Every now and then I spray all my electrical connectors with a contact cleaner/waterproofer spray.
During the last few months, I've had several episodes where the bike would suddenly lose it's power. First time the bike was just parked outside for a couple of hours (no rain), then it wouldn't start.
In 10 minutes I managed to start it, it wouldn't hold a steady idle (stalls), so I had to give it some throttle all the time, but when under load, as soon as I open the throttle more than a little bit, it feels just like if ignition suddenly cuts off, it would bog down. So I was able to ride at 20-30 km/h and after 10-15 minutes everything was back to normal. Since then I've had episodes with similar, but not exactly the same, symptoms.
A few times it happened after I did some water crossing, the bike would stall and won't restart, then finally when it restarted, lose power under load when I open the throttle. So low revs it would work but wouldn't rev higher. Would stall if left to idle, as well. A couple of times during this the FI light would light up, I did a diagnostic self-test and the error code was 21 - crankshaft position sensor. Later at home I checked the wiring to that sensor (no problems), and the sensor resistance was also nominal. Most of the times when this all happens and the bike won't start, the FI light would just flash, but not light up steadily and diagnostic self-test wouldn't not give any error codes (just flashing).
There was also one episode when I was riding rather fast (110-120 km/h) on a very bumpy paved road, and suddenly I lost all the power and had the same symptoms as before.
The last time the bike was working fine for a few weeks (no water crossings or rain during this period), but a few days ago I gave the bike a spray wash with a garden hose, and right after that the same symptoms came, after 15 minutes of riding at low speed the problem disappeared.
Every time this happens, after waiting 10-15 minutes the bike would finally start, and most of the times after 10-15 minutes of riding would start working normally again, but sometimes it would keep doing that power loss and hard starting repeteadly.
All the water episodes make me think the problem might be electrical, but the few times when it happened in absolutely dry conditions still make me doubt that.
I would like to hear anybody's advice on where to look next, and also if anybody had similar stories and what turned out to be the problem.
The worst thing about this is that usually when the bike is in my garage and I try to diagnose the problem, the bike works fine so everything checks out, but obviously something is wrong somewhere, maybe some connector is loose or some wire is damaged in the wire harness (is it really likely under the harness tape wrap?). Or something completely unrelated?
Any advice welcome!
--Gene

 

Hi Gene, welcome to the forum btw

There are many ways to trigger a FI warning light & from my experience 2 different levels of retarding the ignition into limp home mode.

I have had a flashing FI light which caused my bike not to able start at all. This was caused by a completely disconnected sensor.

The second kind on limp home mode was when my secondary throttle butterfly sensor was out of place after i removed the butterfly! This caused the FI red light to stay on continuously & restricts/retards the ignition to stay at the same level as idle & will not advance from there, the bike didn't want rev over 7000rpm without running rough. It took me along time work this problem out & successfully fix it. Now it will rev to 10,500 in 6th gear no problem.

There are many sensors associated with the FI system that could be faulty or just badly connected.

This is a picture of the shaft that runs between the secondary throttle butterfly & it's sensor that got put back in about 45 degrees out of sync, which triggered to FI light as the sensor thought the butterfly was in the wrong position!



Download the FI bike manual from the forum & check through every sensor.

 

The FI light on mine turned on too and it was traced to the O2 sensor but it still starts fine but jerks sometimes. i dont bother to fix it because im gonna remove the FI and install a carb and the big bore.

You can also check your fuel lines or perhaps the fuel filter.

Another option is to send it to your nearest kawasaki dealer so they can run diagnostics by connecting a lap top to the ECU the software should tell you the point of fault. All the best.

 

Thanks a lot guys and happy to make my first post here on the forum (too bad the post is not too cheerful).
I've got the FI service manual and the only time the FI light came in the error code was the crankshaft sensor. Later at home I checked the connector and measured the resistance between sensor leads and everything was nominal. The previous and all the later episodes the FI light didn't come in, so if it is a sensor problem, the ECU is not telling me which one. Some people are telling me it might the fuel pump. Short of buying a new one, not sure how I would test it out, since whenever I'm close enough to my garage to try to diagnose the bike, it works fine.

 

Can KLX's ECU really be hooked up to a laptop? The service manual only talks about self-diag mode which is pretty basic, the FI indicator flashes out the error codes as a series of beeps. I don't think it can tell anything more to a laptop, and that diagnostic didn't give useful info apart flashing that strange crankshaft position sensor error a few times. I don't understand how that sensor can fail a few times then work without problems.

 

Hey Gene, what was the problem. Is your bike fixed. Don't leave us hanging.

 

Hey Graham,
I've just got back to Thailand from visiting my folks back in Russia. I'm planning to have a good time together with my KLX this week and will report back as soon as I have some news!

 

Have you ever changed the plug?

 

I have just had similar problems. Bike miss firing, weak spark, hard to start then suddenly dead. For almost a week I was stuck. I charged the battery and cleaned the injector, tested the coil, Crankshaft sensor, did the whole EFI trouble shooting and self diagnosis. Nothing. New plug, spark plug cap, Nothing.
I then pulled the cover and checked valve clearances. No problem there. Hell I even washed the bike.
Eventually Joel Thailand suggested a common problem. Check the ECU connection.
So I opened all the connecters and plug ins and sprayed WD40.
Bang, fired up first prod of the button. Such an easy fix. ( Hope yours is easy too )

 

Graham, that's lucky you got it sorted. Electrical connector problems have been suggested to me before, I must say I didn't really expect any problems in there, as I clean and check my connectors as my normal periodic maintenance. However, it was suggested that using a contact cleaner with lubricating (for anti-corrosion) properties might affect some sensitive low-voltage circuits, and that I should try a plain (non-lubricating) contact cleaner, which I will do.
I wouldn't use WD-40 on sealed electrical connectors as WD-40 is not rubber-safe and with regular use can eventually swell and damage the gaskets.

Thanks for the tip, already two reports like that is all the more reason to check it out.