2008 won’t idle, tried a bunch, weird issues

New to me 2008 project wr250r, I’ll try to keep this info neat.

Was sold the bike with knowledge that it takes throttle to stay alive. Seller believed it was TPS. Previous owner put wrong piston in and this guy fixed that with new piston, valves, etc.

Ok, so first thing I did was run diagnostics.. TPS was 13/87 which I know is low. I adjusted to 20/97.

Trickle charged battery and bike fired right up but struggled after a few seconds and died.

I ran diagnostics in CO mode, it’s sitting at +4. I threw a new plug in and fired her up. Fired up super fast but what’s weird is the diagnostics “tach” was showing 5000 ish RPM which doesn’t seem right. It would be way louder I assumed. Messing with CO settings had an immediate affect on the bike and kept killing it.

“Idle” screw is all the way in by the way and didn’t seem to have much affect.

Not sure if it’s a symptom of my battery getting drained but at the end of my testing the bike threw er-4 (ecu fault)

Just a symptom of a weak battery?

Not sure what to check next… no apparent air leaks. Haven’t checked valve stuff yet, a little intimidated.

ANY ideas!?

Flynavy wrote:

Previous owner put wrong piston in and this guy fixed that with new piston, valves, etc.

Fired up super fast but what’s weird is the diagnostics “tach” was showing 5000 ish RPM which doesn’t seem right.

“Idle” screw is all the way in by the way and didn’t seem to have much affect.

None of the above sound good, pointing to some fundamental problem(s).

Start with the easiest interventions like a known good battery (could use your car battery), then swap spark plug, check compression, and then start checking all the sensors according to the instructions beginning on page 8-74 of your service manual.

Mega update, hoping for someone smarter than me to chime in!

-valves were out of spec, exhaust was too tight. Shimmed all valves and all are within spec.

- bike fired right up, but wanted to die off idle. Almost seemed fuel starved. I have TPS at 22/97 and CO at 4.

-I needed to remove exhaust to check something and when I put it back and started it sounded awful, threw overheat light, smoked like crazy. I found I’m missing exhaust header gasket completely and also bolt for muffler to header clamp. Please don’t flame me, but how much affect would a “loose” exhaust have on fuel/richness?

-pulled plug, it’s very very dark. Brand new plug that’s been ran for maybe 5 minutes for these tests.

-then did compression test (I’ve already went down the rabbit hole on how accurate this can be but the manual had a procedure)

Read 50PSI ice cold. Added a little oil and read 105PSI. I don’t want to assume it’s rings or something else. Is it even possible to check with engine on the bike?

My overall shade tree mechanic thoughts are it just seems really really really rich, reaks of gas when trying to run, black plug, etc.

Is the ER-4 code gone? What did you do to make it go away?

In your original post you said that the previous owner installed new piston, valves, etc. Given your findings of valves out of spec and low compression, you have to conclude that the previous owner either lied or did a horrible job; in either case you have to get into the motor and check the state of piston and rings.

Having said that, low compression does not result in the motor running rich, and neither do the exhaust problems you have encountered. I presume you have already checked the air filter and the air intake to make sure there are no obstructions, and the same is true for the exhaust system?

If the previous owner swapped the fuel pressure regulator for the Quantum one (the only aftermarket unit available), then the bike would be running rich, but not to the degree you are seeing. A sensor completely out of range could be responsible, but in that case I would have expected a Fault Code to show up; still, checking all the sensors and components starting on page 8-74 seems the best way to troubleshoot this.

johnkol wrote:

Is the ER-4 code gone? What did you do to make it go away?

In your original post you said that the previous owner installed new piston, valves, etc. Given your findings of valves out of spec and low compression, you have to conclude that the previous owner either lied or did a horrible job; in either case you have to get into the motor and check the state of piston and rings.

Having said that, low compression does not result in the motor running rich, and neither do the exhaust problems you have encountered. I presume you have already checked the air filter and the air intake to make sure there are no obstructions, and the same is true for the exhaust system?

If the previous owner swapped the fuel pressure regulator for the Quantum one (the only aftermarket unit available), then the bike would be running rich, but not to the degree you are seeing. A sensor completely out of range could be responsible, but in that case I would have expected a Fault Code to show up; still, checking all the sensors and components starting on page 8-74 seems the best way to troubleshoot this.

Thanks for the reply! The ER4 was caused by a weak crappy battery, currently have a new 10A on there, no code.

The bike wants to start and will start. I crack some throttle to keep her going and the RPMS oscillate like she’s starving for fuel. A little bog then they shoot up and the cycle repeats. This is a new OEM pump so I rule that out. I know injector has been bench tested and shouldn’t be the issue. I can’t think of anything else. Smokes pretty good, still smells very rich on the fuel. Any ideas?

Another data point for what it’s worth… went to see if any codes were stored (none) but on TPS screen it’s eradically bouncing between 30-33 on the screen with zero hands on the bike.

Also tested battery and charging. About 12.6 starting and 13.1 when I had it running. Could stator issues cause issues im seeing at all?

You also reported that the RPM function was out of whack (showing 5000 while idling), is that fixed too with the new battery?

The erratic engine behaviour you describe points to a major problem like fuel or air delivery, but you say you have already checked fuel pressure, fuel injection, air delivery, and spark. Compression is a problem, but it wouldn't create the ups and downs that you see.

I would say try the no-cost checks first, like all the sensors and sub-components starting on Page 8-74, but I really can't think of how a malfunction of one of them would produce the symptoms you have.

Is the 13.1V while running at idle or higher up? It should be around 14V when revved (about 5000 RPMs), but again that wouldn't create the problems that you see.

Has the stator recall been done? I can see how an extreme stator issue could have damaged your R/R resulting in the issues you experience, but it is a stretch; still, checking the stator is relatively easy, Page 8-76.

Is the TPS moving while engine RPMs fluctuate?

johnkol wrote:

You also reported that the RPM function was out of whack (showing 5000 while idling), is that fixed too with the new battery?

The erratic engine behaviour you describe points to a major problem like fuel or air delivery, but you say you have already checked fuel pressure, fuel injection, air delivery, and spark. Compression is a problem, but it wouldn't create the ups and downs that you see.

I would say try the no-cost checks first, like all the sensors and sub-components starting on Page 8-74, but I really can't think of how a malfunction of one of them would produce the symptoms you have.

Is the 13.1V while running at idle or higher up? It should be around 14V when revved (about 5000 RPMs), but again that wouldn't create the problems that you see.

Has the stator recall been done? I can see how an extreme stator issue could have damaged your R/R resulting in the issues you experience, but it is a stretch; still, checking the stator is relatively easy, Page 8-76.

Is the TPS moving while engine RPMs fluctuate?

Your replies are what keep me going. Thank you, seriously. Trying not to spool up to much with info but this is the latest..

Walked into garage, cranked bike… fired up immediately no hesitation. Smooth idle. Volts on battery went from 12.7 to around 13.0. About 6 seconds later the bike died, but it was extremely abrupt like the spark just left.

I did run my VIN and it says recall performed, but my next test is on the stator. I think the bike is clearly getting fuel, as I rev to keep it alive it reeks. Is it possible I’m forcing it to stay going but the electrical side can’t keep up?

Sudden death means absence of either fuel or spark; you have checked both and confirmed they are working fine, so there aren't a lot of options left.

Low compression may also result in sudden death, but how low is "Low"? At only 50 psi I would expect a lot of unburned fuel, which could explain the strong gas smell, but is it too low to sustain continuous running? I don't know.

Would the engine carry on running if you applied steady throttle? For how long?

If you have exhausted checking all sensors and sub-components, then the expensive troubleshooting begins: start replacing components one-by-one, ignition coil, R/R, injector, ECU, etc. Is this more onerous than tearing into the engine and addressing the low compression?

johnkol wrote:

Sudden death means absence of either fuel or spark; you have checked both and confirmed they are working fine, so there aren't a lot of options left.

Low compression may also result in sudden death, but how low is "Low"? At only 50 psi I would expect a lot of unburned fuel, which could explain the strong gas smell, but is it too low to sustain continuous running? I don't know.

Would the engine carry on running if you applied steady throttle? For how long?

If you have exhausted checking all sensors and sub-components, then the expensive troubleshooting begins: start replacing components one-by-one, ignition coil, R/R, injector, ECU, etc. Is this more onerous than tearing into the engine and addressing the low compression?

I have not tried all tests yet if I’m being honest. But here’s the latest…

Stator has slight burn marks. I went to pull plug that goes into voltage rectifier and one of the leads wasn’t even connected. I couldn’t reconnect it because it was too corroded. Smoking gun? I know a bike can run with no rectifier but that plug is what you test for stator continuity right? Am I on to something?

Flynavy wrote:

I couldn’t reconnect it because it was too corroded.

You mean that pin was so corroded you could not push the plug into the socket? What was the reason for the pin not making contact? Was it pushed back into the housing, or was it bent? Could you clean the pin, maybe scrape the corrosion off? If not, you can find virtually any connector at Cycle Terminal.

Could you at least connect a probe to it to measure the stator coil resistance?

I don't know if this a smoking gun, but you should definitely address this before you move to further troubleshooting.

It used to be true that a bike would run without the rectifier working (essentially running off the battery), but with modern bikes where the ECU controls everything, I don't know how well a bike would run like this.

johnkol wrote:

Flynavy wrote:

I couldn’t reconnect it because it was too corroded.

You mean that pin was so corroded you could not push the plug into the socket? What was the reason for the pin not making contact? Was it pushed back into the housing, or was it bent? Could you clean the pin, maybe scrape the corrosion off? If not, you can find virtually any connector at Cycle Terminal.

Could you at least connect a probe to it to measure the stator coil resistance?

I don't know if this a smoking gun, but you should definitely address this before you move to further troubleshooting.

It used to be true that a bike would run without the rectifier working (essentially running off the battery), but with modern bikes where the ECU controls everything, I don't know how well a bike would run like this.

I can try, there’s just nothing for the loose connector to “bite” into on the plug if that makes sense. I also don’t have the fanciest of meters (and by my research this will definitely matter) so I’ll see about borrowing a more precise meter.

Even something like the TPS reading all wacky in its own is telling me something electrical. But I know I shouldn’t get excited and really need to test one by one, as you’ve repeatedly asked if I’ve done!

Hang in there with me I think we are on to something.

Flynavy wrote:

I can try, there’s just nothing for the loose connector to “bite” into on the plug if that makes sense.  I also don’t have the fanciest of meters (and by my research this will definitely matter) so I’ll see about borrowing a more precise meter.

I can't really picture what is going on with the pin, but it doesn't matter. As long as your meter can read milli-ohms you're good.

johnkol wrote:

Flynavy wrote:

I can try, there’s just nothing for the loose connector to “bite” into on the plug if that makes sense.  I also don’t have the fanciest of meters (and by my research this will definitely matter) so I’ll see about borrowing a more precise meter.

I can't really picture what is going on with the pin, but it doesn't matter. As long as your meter can read milli-ohms you're good.

I can’t seem to upload photos… grrr I’ll try on my PC later.

Someone has been in the bundles, bunch of shoddy solder jobs and tape to hide it. Horn, and a few others near the rectifier. The mystery unfolds.

Stator has an area where it’s black, not like OMG it’s insane looking but something of note.

I can’t get a reading on that connector per the manual, I’m assuming it’s user error.

Flynavy wrote:

Someone has been in the bundles, bunch of shoddy solder jobs and tape to hide it.

That is not good, but it's consistent with the shoddy work on the piston and valves.

Flynavy wrote:

I can’t get a reading on that connector per the manual, I’m assuming it’s user error.

At this point I don't think you can assume anything; is it out of the scope of possibility that the previous owner cut some wires without bothering (or trying and failing) to reconnect them?

johnkol wrote:

Flynavy wrote:

Someone has been in the bundles, bunch of shoddy solder jobs and tape to hide it.

That is not good, but it's consistent with the shoddy work on the piston and valves.

Flynavy wrote:

I can’t get a reading on that connector per the manual, I’m assuming it’s user error.

At this point I don't think you can assume anything; is it out of the scope of possibility that the previous owner cut some wires without bothering (or trying and failing) to reconnect them?

I’ll try to simplify what I think is going on… and I forgot a critical detail.  By coincidence I know the owner before the guy I got it from.


My acquaintance got the bike in rough shape, wouldn’t idle well.  He replaced fuel pump, cleaned injector, and then put the wrong piston in assuming low compression.  Used a WR250F piston (5 valves) and it bent a valve and wasn’t good.

Next guy fixed bad piston, replaced valves, timing chain, and gaskets, but still wouldn’t idle, assumed it was TPS and sold it as is.

I think whoever had it before these two is the one messing the wires but who knows.

I was able to get my meter to read ohms but it was so egregious it wasn’t even close.  But it did pick up resistance on the stator so my next step is fresh stator this coming up Monday.

Photos!

Ok first pic is condition of the stator plug.  It wasn’t fully loose like you see but it basically fell out, and any attempt to push back in failed.  Regardless I hit that that pin with the meter with the other ones and it seemingly failed. 

What’s this little fuse do? Here’s an example of the wiring I found.

That female pin looks fine; is this the one that you cannot push back into the housing? There is also no corrosion I can see on it, is it the male pin that is corroded?

You're right, the stator wiring does not look burned; did you get low readings on all three combination, or just one?

The second wire picture shows a pink and a brown, which may be the ones for the horn (although the electrical diagram shows pink and white for the horn). The first picture shows a red (or is it pink?) and a black; I can't readily identify these, do you have a sense of where they're going? In any case, shorting them like this with a fuse is never a good idea.

The history of the bike sounds troublesome; since you mentioned it, did you check the timing when you were adjusting the valves?

Flynavy wrote:

The one with the fuse… I’m assuming someone did some sort of bypass mod maybe for the kickstand safety? Because I can start the bike with it down.

The kickstand safety mechanism does allow you to start the bike with the kickstand down, but it will turn the bike off if you try to put it in gear; try that and see what happens.

If you got bad readings on all three combinations, then a new stator is definitely needed.

johnkol wrote:

Flynavy wrote:

The one with the fuse… I’m assuming someone did some sort of bypass mod maybe for the kickstand safety? Because I can start the bike with it down.

The kickstand safety mechanism does allow you to start the bike with the kickstand down, but it will turn the bike off if you try to put it in gear; try that and see what happens.

If you got bad readings on all three combinations, then a new stator is definitely needed.

Forum is being weird allowing photos.  I was able to identify the wire I think, neutral switch? Not fully understanding what it does.

Last thing I found was this bundle of wires.  I can’t tell if this is a factory thing or after the fact, any ideas?