KLX250 intermittent power loss, hard starting

Discussion in 'Technical' started by heilong, Jan 25, 2014.

  1. 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!
  2. Let the Kawasaki Dealer take a Look at it? They can plug into the Computer and reset things? Good Luck.
  3. Gene,

    Had a similar problem, changed the spark plug and all is good again :)
  4. Back to Thailand in July, bike is waiting for me, can't wait to look into that problem again.
    Thanks for suggestions!
  5. Hi Gene, I have in the past run across several electrical waterproofing sprays that gave me similar problems on fuel injection systems. Seems they would coat the connector pins and cause resistance and intermittent loss of contact. Signal voltage is very low and ecu's are sensitive, so it doesn't take much.
    You might try cleaning it out of your connectors, I just used brake cleaner, and see if that does it. I switched to using Dielectric grease between the connector halves only, not on the terminals, sealed where the wires go through the rubber boot on the back of the connector with silicone sealant, and that solved the troubles I had..
    Good Luck! Rj
  6. Hey Rj,
    Interesting tip, I will try that. I saw several "contact cleaner" sprays on the market that mentioned that they contains no oils whatsoever (so pure cleaners) - I wondered why they list that as a feature/pro. The contact cleaner I used mentions water-resistance and corrosion-resistance qualities. I've never had problems using this kind of spray with my last (carb bike), but what you mention about ECU/sensor voltages and possible resistance problems makes sense. I will try some cleaner on all the sensor and ECU connections, and keep using the waterproofing spray on stuff like the voltage regulator, power relays, headlight etc. and other high-current connectors.
  7. Just a guess, but it's something I've seen so hope it does the trick for you!
  8. Well I've heard many guesses already, will try them all and hope one of them does the job. Proper way would be to try them one-by-one to isolate the problem, however since it's so intermittent and I just want the bike working fine ASAP, I'll probably try all the guesses I've heard at once.
  9. Got the bike sorted out. Found a bunch of problems.
    1) I found some info that the ECU connector lead is prone to chafing on the 2009 model bikes, a forum posting even mention there was a recall about that, and the newer part number for the wiring harness has that problem fixed by wrapping the ECU connector lead in electrical tape almost until the connector itself. On mine, a couple of wires had their insulation chafed through to the bare copper, some of the copper strands broken and the rest had minor corrosion. One of the wires was from the crankshaft position sensor - if the ECU doesn't get proper signal from this sensor, I doubt the engine can work at all. I had the FI indicator light showing "error 21" which is the crankshaft position sensor a couple of times, but not always, when the bike failed to start. Couple more wires had insulation partially chafed through, but copper still not visible. Fixed by soldering and heat-shrink tubing (disassembled the ECU connector and release the affected wires' terminals to get access). I verified each and every circuit continuity on the bike with a multimeter. Took a while with the wiring diagram, but felt pretty satisfying.
    I also found several wires chafed on the leads coming to the fuse holders and started circuit relay. Don't know what exactly did that damage because these leads stay between the airbox and the black plastic fender part, no sharp edges there, just rubbing against the plastic for many thousands of kilometers I guess. Again, insulation was worn through and half of the copper strands were broken, no corrosion though. Fixed by soldering and heat-shrink tubing.
    After all the wiring was fixed, I cut some high-temp PVC sheathing lengthwise and cover the leads with that, then taped over with nice 3M electrical tape. The ECU connector lead I wrapped with a more flexible but really thick and tough 3M rubber splicing tape, then overwrapped with the electrical tape.
    Pics of somewhat damaged ECU connector wiring:

    2) I didn't expect any problems there, even I was almost too lazy to check with a multimeter, but luckily I was too anal about that, so I did check and to my surprise the Engine Run switch was intermittently not working in the RUN position. Push on the button a bit more and there was a connection, let go and sometimes the multimeter would keep beeping, sometimes it would stop. I always figured these switches are well sealed and never fail. Got the switch housing open, disassembled the switch, it looked a bit dirty but not that bad. Cleaned everything, touched up the contact points with 400 grit sandpaper, put just a thin film of dielectric grease on everything and reassembled, problem solved. Actually I figure it might have been THE main reason why my bike quit running or wouldn't start intermittently. I'm in the habit of always using the Engine Run switch to kill my engine when I stop riding, just to get this good habit for situations when I need it (when going down) - might be that contributed to developing this problem.

    3) The piston rings were worn, piston had a lot of deposits, valves had a lot of deposits, the exhaust valves had deep pitting and their seats also had minor pitting. The bike definitely had low compression and the cam chain was noisy.
    I got a new piston, rings and pin a while ago, I got a local mechanic deglaze&hone the cylinder for me, actually with this cylinder and the new piston and rings the clearances and ring end gaps are pretty loose, still within service limit but not that good. However having no spare cylinder - and a new one is not on the budget for now - I decided to install things as is and hope it will last long enough until I get another cylinder. New exhaust valves, cleaned the intake valves, my wife did the valve lapping, new valve stem seals, cam chain and tensioners, put in a krieger manual cam chain tensioner as well. Did the Marcelino cam timing mod, disabled ACR with a bent piece of thick steel wire replacing the ACR spring.

    My swingarm bearings were shot, got the old ones out - they almost fell out with one hit with a hammer, found out the bearing holes are damaged, especially the outside part where the seals sit. Tried new seals in there - I could see a gap of at least 1mm. Since a new swingarm is pretty cheap here in Thailand, and the old one also had some deep (>2mm) groove cut with a completely worn-out sidestand (previous owner legacy), I decided to get a new one, put in new bearings, sleeves and seals. Also a pair of shock arm bearings were rusted (actually I found that out earlier, but having no replacement bearings put a bunch of grease in there and rode it like that for a month). Replaced all the shock arm bearings, sleeves and seals.
    I'm 80kg, often carry my wife as a passenger, and a bunch of travel gear or grocery shopping, the stock spring is too soft, but I cranked up the preload to 121mm (measured according to the manual), close to the manual specified limit of 123mm, that's 13.5mm more preload than standard (107.5mm), bike feels much better now and doesn't sag under the weight of passenger&luggage. With just me on the bike, no gear/luggage, I have a rear rider sag of 58mm (25% of full travel), obviously more with riding gear etc. However, bike sag is basically zero - ideally I should get a harder spring. I don't know why I never bothered to adjust preload before, it's not difficult and is useful adjustment. I should get a shock wrench though, a punch and a hammer took a while to turn the adjuster ring 9 full turns.

    Anyway, 100 days since I started the rebuild, I fired up the bike, it came to life so quickly. Gave it a hard break-in, changed the oil after 30km, did another hard day of riding today (going grocery shopping). Feels great to ride again. The bike's sound somewhat different than before as well.

  10. Even after rebuild, bike's still burning some oil. Looking for a new cylinder...

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