KLX250 intermittent power loss, hard starting

[heilong]

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

 

[bsacbob]

Gene, I had similar symptoms on my KLX on a recent dirt ride, after disconnecting the side stand switch and the clutch sensor i was at a loss, eventually found the problem under the seat, one of the connectors next to the fuse block had worked open making intermittent contact causing the motor to stall when the clutch was engaged or make the bike kangaroo down the road.

Maybe as simple as that, but it sounds like some electrical issue.

 

[heilong]

Thanks, I've checked these connectors already, no problems there. I haven't checked the sidestand switch, though. Next time if I get this problem I'll see if shorting the sidestand switch connector would help it to go away. One more thing in the list of things to check.

 

[alexuk]

does it happen with a full tank?

could it be the pipe blocking up with packing coming loose?

 

[heilong]

Most (or at least some) of the times, the tank was at most half full.
You mean the exhaust pipe packing? Is it possible to cause such intermittent issues that disappear completely then reappear somewhat randomly?

 

[Harrythefinn]

Quite a few similar reports on earlier FI Husabergs , it was the fuel pump either getting hot and partially siezeing (would work OK when cool) or just not working properly. If not the pump, then it could be contamination in the fuel system, clogging the injector.

 

[alexuk]

Possibly if there is a blockage in the tank breather system,worse as the tank empties, a vacuum inside could prevent fuel getting to the engine

With the exhaust packing, it may come loose and block the exhaust, so little power, but you would probably notice it flying out of the exhaust as power returne to normal. Next time it happens just check that the exhaust is not blocked

 

[heilong]

Was thinking about the fuel pump, as I had similar symptoms on an old EFI car long time ago.
Any way I can test the pump, short of replacing with a new one?
Last time I checked, the breathing hoses were free of obstruction, but I'll blow them out again with a compressor.

 

[Harrythefinn]

Is there a way to get the fuel line off near the injector and put a gauge on it? Can you hear the pump working when you have the problems? I would probably buy a new pump and it would always be a spare if it is not the problem.

 

[LivinLOS]

Quite a few similar reports on earlier FI Husabergs , it was the fuel pump either getting hot and partially siezeing (would work OK when cool) or just not working properly. If not the pump, then it could be contamination in the fuel system, clogging the injector.

I had a intermittent fuel pump in the blade a couple of years ago.. Was baffling as it always came back to life after a period so real hard to debug.

Left me stranded a couple of times which had me fuming. Such a simple thing but annoying as all hell.

 

[heilong]

I don't have a special gauge, the hose has some special quick-release connector, not sure what kind of gauge could work here. Replacing the pump is one option, not very cheap though. So I want to do as many cheaper tests first, before going for it.
As for hearing the pump, when I turn on the bike, it always make some cute sound. I always thought it's the pump activated. Recently, I had the tank completely off the bike to test some stuff, and turning on the ignition makes the same sound, I really wonder if that's some kind of air suction valve self-test or something else, but definitely not the pump. Therefore I have no idea what the pump is supposed to sound like (normal or misbehaving one!). I'll try to turn on the bike with the tank off but pump connector plugged in, and listen closely what it sounds like.
LivinLos, how did you narrow the problem down to pump failure? Or did you just replace it and after that realized it was indeed the pump's fault?
Thanks for the feedback, guys!

 

[Captain_Slash]

Isnt that noise when you turn the ignition on the FI?

I always get a noise on a FI bike

 

[heilong]

I always thought it's the pump but that's something else. Take off the tank and turn the ignition on, same noise.

 

[heilong]

Found out that noise is the self-test of the secondary throttle actuator in the throttle body. Pump also makes a little noise.

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.