2013 TXC 250 starts cold, stalls hot, then won't start.

[Trenchcoat85]

durt (kurt? I like that)- seems like we've solved a small handful of problems, with the exception of the hot re-start situation. I'm still thinking it's lean (starter fluid indicates that). You've pretty much eliminated every other heat-related possibility like the coil, pulse-coil, cts, fuel pump, etc- do you agree? I'm not sure a re-map is gonna help you (TXCs have the race stuff) but ZipTy does have a modified map that may or may not help ($40, and insure your ECU. call first, they need a bike to install it on)

your idle is fine to my ears (end of May video reference), not too high so don't worry (1950rpm is stock, 2100 is better imo). My TE idle hunts a bit when warm; i don't sweat it. I do, however, have to give a tiny bit of throttle when starting almost always 'cept in very cold temps or when the cold start is used. my bike kickstarts very easy- hot or cold (and no throttle necessary).

some questions:

• is there a re-starting difference when hot between using the kill button and stalling the motor?
• how does your bike kickstart- hot or cold?
• does using the cold start help during hot re-starts?
• have you tried cracking the throttle a bit?
• inspect and tighten the intake manifold (again?)
• tighten the header bolts (14mm hex IIRC)
• next time you check the valves, put a socket on the head bolts and put a tightening torque on 'em 15+lbs maybe. (btw, I think your valves are good now. check 'em in a couple of months)
• are you consuming coolant or oil? or is the oil frothy/milky? (head gasket)

Do you agree that the bike is lean down low? Since you inadvertently did the TPS adjustment, lets try that again (using different voltages- maybe range 'em from 0.550v to 0.800v and see where the bike likes to live). It would be interesting to see if your baseline tps voltage is the same during hot re-starts (and if not... maybe a failing tps?)

I hate to mention this last because it's what people retain after reading: I wonder if your ATS is failing (in the airbox). I have never heard of this (ever) but who knows? If it's the same as your cts, you could stick your spare one in there (but this is unlikely). ...ok, now forget I wrote this paragraph.

excellent feedback and reporting btw; that makes following this thread easier.

 

[durtkillon]

Durtkillon is code for Kurt Dillon.

• is there a re-starting difference when hot between using the kill button and stalling the motor?
• how does your bike kickstart- hot or cold?
• does using the cold start help during hot re-starts?
• have you tried cracking the throttle a bit?
• inspect and tighten the intake manifold (again?)
• tighten the header bolts (14mm hex IIRC)
• next time you check the values, put a socket on the head bolts and put a tightening torque on 'em 15+lbs maybe. (btw, I think your valves are good now. check 'em in a couple of months)
• are you consuming coolant or oil? or is the oil frothy/milky? (head gasket)

Do you agree that the bike is lean down low? Since you inadvertently did the TPS adjustment, lets try that again (using different voltages- maybe range 'em from 0.550v to 0.800v and see where the bike likes to live). It would be interesting to see if your baseline tps voltage is the same during hot re-starts (and if not... maybe a failing tps?)

I hate to mention this last because it's what people retain after reading: I wonder if your ATS is failing (in the airbox). I have never heard of this (ever) but who knows? If it's the same as your cts, you could stick your spare one in there (but this is unlikely). ...ok, now forget I wrote this paragraph.

There is no difference between stalling and killing it when hot. Once it's hot, it can't seem to fire up. By the way, the bike is not stalling anymore. The only problem I have left is the hot start issue. There is an occasional mild backfire pop on deceleration, but only when I'm grabbing 1/2 throttle and letting it go. I think that's normal.

The bike will kick start cold, but not hot. From cold, it's not a two kick bike, more like 6 kicks experimenting with the cold start lever. Otherwise, the symptoms are the same as the starter.

The cold start does not help during restarts. It makes it worse.

I've tried cracking the throttle, but that does not help. I've tried cracked, 1/4, 1/2, Full. Nothing helps.

Header bolts are tight and no sign of leaks.

I'll check the torque on the head soon. I'm becoming a pro at tearing in to the valves at this point.

I like the TPS idea. I'll test it hot and see if it's different.

I agree that it the bike acts lean down low. The starter fluid test and messing with the JD tuner supports that. I nearly maxed out the idle richness (per the recommended setting) and the throttle response improved tremendously off idle. Prior to that, it had a lean bog if I grabbed 1/2 throttle, like it's jetted too lean.

There is a small oil leak at the clutch cover. I haven't ridden enough to know if it consumes oil over the long haul, but there is no smoke at the tailpipe, hot or cold.

The coolant is deep blue. The owner told me it's ICE. Looks fresh to me from the top of the filler cap. I'd need to drain it to be sure.

I have not explored the ATS yet. I know nothing about them, but I imagine it's just a resistor. I could test it with a heat gun. I'll check the manual to see if there is a procedure. I believe the CTS to be a normally open switch that kills the motor if it's too hot. That is just a guess, though. The bike ran fine with the CTS disconnected today.

Thanks again for the ideas!

 

[Trenchcoat85]

don't overlook the manifold tightening/inspection too.

The bike will kick start cold, but not hot. From cold, it's not a two kick bike, more like 6 kicks experimenting with the cold start lever. Otherwise, the symptoms are the same as the starter.

hmmm, it should actually start easier- the kickstarter spins the motor faster. Unless, of course, you're cranking the starter 10+ seconds when cold. Meaning 6 kicks is an improvement over the e-button.
try putting a fuel pressure gauge on the fuel line (i don't think it matters if you "tee" it or not in this case). I think we need to see at least 30lbs; and IIRC 42lbs is spec. Maybe the pressure regulator is failing or there's an undiscovered crack somewhere.

This is a good point to remind you and future readers that I am not a fuel injection expert. I quit working on cars in the late-80s when FI was starting to become prevalent. I've learned 80% of my FI knowledge from my bike and the good folks here.

The cold start does not help during restarts. It makes it worse.

makes it worse? I am guessing you mean you have to crank longer maybe? or better put: what's the criteria for "worse"?
also- during the next hot re-start situation, take a whiff of the exhaust to see if you smell lots of unburned fuel. And does the bike ever start to "catch" or crank faster?

I've tried cracking the throttle, but that does not help. I've tried cracked, 1/4, 1/2, Full. Nothing helps.

hunh. my technique, btw, is to open the throttle my 1/4, then hit the button and roll OFF the throttle... the sweet spot is somewhere down near "cracked" and as the throttle closes past that spot the engine catches.

I like the TPS idea. I'll test it hot and see if it's different.

ok, sounds good. The failing tps is just half of that theory; the other half is that at sometime it was inadvertently set it lower than the bike wants to be at.

I agree that it the bike acts lean down low. The starter fluid test and messing with the JD tuner supports that. I nearly maxed out the idle richness (per the recommended setting) and the throttle response improved tremendously off idle. Prior to that, it had a lean bog if I grabbed 1/2 throttle, like it's jetted too lean.

This supports the TPS theory. The bike is in the wrong area of the map maybe. Lets raise the tps voltage to, say, 0.700v and see what happens. Your JD may be way-overcompensating for a poor tps setting; your bike should run strong without it, normally.

There is a small oil leak at the clutch cover. I haven't ridden enough to know if it consumes oil over the long haul, but there is no smoke at the tailpipe, hot or cold.

The coolant is deep blue. The owner told me it's ICE. Looks fresh to me from the top of the filler cap. I'd need to drain it to be sure.

This was just a head gasket hint; these observations sounds like you're good.

I have not explored the ATS yet. I know nothing about them, but I imagine it's just a resistor. I could test it with a heat gun. I'll check the manual to see if there is a procedure. I believe the CTS to be a normally open switch that kills the motor if it's too hot. That is just a guess, though. The bike ran fine with the CTS disconnected today.

resistor: yep (although my schematic shows it as a capicator- and I'm pretty sure thats a mistake 'cause it shows the condensor as a resistor: so diagram mix-up.
CTS- nope, it would be a resistor too. (however the fan switch- if you have one, would be a bi-metallic N/O switch). the ECU wants/needs continuous temp readings
Careful with the heat-gun... low settings are usually in the 600° F range. Your finger heat should be enough to change the resistance.

 

[R_Little]

I've the thread and I can tell you from my experience with the black heads the TPS has to be set correctly.

It moves the whole map up and down at a given throttle opening and will make your motor idle lean (or rich) if set incorrectly.

Is there and adjustment?

 

[durtkillon]

I tried a few more things, but still have the issue. I'll answer questions first, then provide an update.

E start fires up pretty quick when cold, whithin a second. Kick starting does not come easy on this bike. I've tested that a few times.

I am guessing you mean you have to crank longer maybe? or better put: what's the criteria for "worse"?
also- during the next hot re-start situation, take a whiff of the exhaust to see if you smell lots of unburned fuel. And does the bike ever start to "catch" or crank faster?

I should have described that better. If I start the bike and let it run for say 20 seconds, then kill it and pull the cold air knob, it will not start. If I push it back in, it will start, until it gets hot (say 170 deg F). Once the hot start is active, the exhaust does not smell terribly of un-burned fuel, but it is detectable in the slightest way I can describe.

my technique, btw, is to open the throttle my 1/4, then hit the button and roll OFF the throttle... the sweet spot is somewhere down near "cracked" and as the throttle closes past that spot the engine catches.

Tried this under hot start conditions and no luck.

This supports the TPS theory. The bike is in the wrong area of the map maybe. Lets raise the tps voltage to, say, 0.700v and see what happens. Your JD may be way-overcompensating for a poor tps setting; your bike should run strong without it, normally.

I was exited about this idea, but it did not bear fruit. I started the bike with the volt meter on the tps test harness. Fired right up cold and read 0.684 volts. I stopped and started it 3 or 4 times and each time it read 0.684. Then I let it idle and heat up to the hot start condition. It still read 0.684. Then I made a series of adjustments from 0.45 to 0.80. The bike would not restart under any of the conditions. I think the TPS is working OK.

 

[Trenchcoat85]

aw, shoot... I was actually hoping that the TPS adjustment experiment might show some results. I did not actually think your tps was defective but it was a free test.

It's a little confusing that the tps adjustment did not have any noticeable effect over such a wide range of voltages. btw, i would *guess* that 0.680v is an adequate setting for a closed throttle.

I might take the jd out of the loop and get the bike running, if possible. and hot-startable. Then add the jd back in once we've got a working baseline.

it still sounds like we're lean; the question now i guess is how is the air sneaking by the map sensor... assuming the map sensor is good- and it should be. is it possible we've got a slightly burnt or slightly open exhaust valve or maybe a bad or cracked seat/head?

on the TB: has the mechanical throttle stop/cable adjustment been messed with? I believe (but do not know) that the throttle plate should be completely closed with no throttle. (a review of your pictures shows that without cables the throttle plate is closed; so maybe you wanna just look at the cable adjustment i guess)

this is becoming a head-scratcher. I suppose getting the rest of the problems worked out is a victory, but... damnit, I want this thing to start hot.

btw, can you bump-start it downhill when hot?

 

[Trenchcoat85]

"See, I'm an idea man, Chuck. I got ideas coming at me all day... I couldn't even fight 'em off if I wanted. Wait a second... hold the phone! Hold the phone!..."

here's an easy outside-the-box experiment: use scotch tape and tape up the inlet hole of the cold-start circuit. Start 'er up (if it will) and then see how it does a hot re-start.

might need some throttle for both hot and cold starting. I would not run at super high throttle settings for fear of sucking in the tape (but I don't think there would be any damage really).

if there is big (and positive) changes, maybe the cold start circuit is defective (any o-rings?), or has a leak, or is way out of adjustment, or the TB has a crack.

(maybe I should call this circuit more of an air-bypass thing, since the cold start feature is a very minor part of it's functionality)

maybe wait a day or two and see if anyone has a good reason to not do this. I don't want you to f*ck up your bike because of my stupidity.

 

[durtkillon]

I'm going to investigate the throttle cable and hard stop. The cable adjustment screw is nearly all the way out on one cable. I didn't think it was an issue because I hear the "tink" sound when I let go of the throttle. I presumed that was the plate closing on the throttle body, but I wonder if it's the hard stop keeping the plate open...making it lean.

Hold my beer....

 

[Johnrg]

I wonder if you have a dyno locally that can do a AF measurement? Also it could be your map got corrupted on the ECU. If the cost is minimal to reflash at ZipTy, that may be the best way to isolate the map as an issue. Clearly it is running but seems like mapping is whacked based upon corrupted AF ratio at certain temps? The JD may have always been a bandaid. I know my initial stock map was faulty and reflashed it worked better albeit with open cage installed too. Last thing is maybe the ignition timing is screwed up somehow?

 

[durtkillon]

I just sent an inquiry to ZipTy to see if they can reflash the ecu. Maybe they can test it as is to help with troubleshooting.

 

[Trenchcoat85]

I just checked my throttle play at the grip and it was quite a bit- maybe 5 or 10°

So I looked up the freeplay in the manual. On the open-cable (throttle cable, pull cable in older parlance- the one with the blue marker) it is supposed to be 3mm at the throttle body. The close-cable (idle cable, push cable. and I gotta admit i like the italian "open and close" although its a bit clumsy in 'merican) is a tight 1mm. I am used to the close-cable being looser, but that really does not have any bearing on your issue.

After researching a jazzillion keihin throttle bodies for another thread a couple of months ago, I found out that on our style of tb (with the bell crank that the cables hook to. And I have no idea why it's like that) there are 2 or 3 different options for the mechanical stop of the throttle plate that manufactures' can specify. Some KTM race bikes actually have a thumb screw for quick manual adjustments, in place of our allen set screw. which BTW, maybe should have paint on it to indicated if it's been "screwed" with. All this is under the black dust cover.

A jazzillion keihin throttle bodies is around 30, it turns out.

I would put a chunk of slack in both cables just to eliminate any uncertainty. Later, when everything is good, you can adjust it out.

 

[durtkillon]

Well, I have made an interesting discovery. When I took the TB off again to inspect for leaks and check the cables and cable stop, it was abundantly clear that somebody had been here before. The accelerator cable was adjusted obnoxiously far out, which should just take up the slack, but I thought, "no biggy, I can hear the throttle plate tick". It must be closing all the way right? Well, when I opened the cover for the cables, I noticed the factory "don't adjust this" paint on the hard stop had been messed with and the adjuster bolt was really marred up from vice grips or the like. This was holding the throttle plate open just a crack. I verified this by blowing through the throttle body and holding my thumb over the cold start bypass. I then adjusted it to where the plate just closes completely and blew through it again. It is now clearly blocking air flow.




This would explain a lean situation at idle!


So I put the bike back together and same problem persists. It fired up cold, but would not hot start. Without the JD, it seems to still have the lean bog if I grab copious throttle. I replaced the air horn, because I figure that is only making things leaner without it.

It runs best with the JD tuner running fat at idle and 44 clicks on the cold air bypass. I messed with the TPS some more, but not much change really.

I thought I found the smoking gun, but I was not that fortunate.

 

[Trenchcoat85]

Well, I have made an interesting discovery. When I took the TB off again to inspect for leaks and check the cables and cable stop, it was abundantly clear that somebody had been here before. The accelerator cable was adjusted obnoxiously far out, which should just take up the slack, but I thought, "no biggy, I can hear the throttle plate tick". It must be closing all the way right? Well, when I opened the cover for the cables, I noticed the factory "don't adjust this" paint on the hard stop had been messed with and the adjuster bolt was really marred up from vice grips or the like. This was holding the throttle plate open just a crack. I verified this by blowing through the throttle body and holding my thumb over the cold start bypass. I then adjusted it to where the plate just closes completely and blew through it again. It is now clearly blocking air flow.
View attachment 80440
View attachment 80441View attachment 80440


This would explain a lean situation at idle!


So I put the bike back together and same problem persists. It fired up cold, but would not hot start. Without the JD, it seems to still have the lean bog if I grab copious throttle. I replaced the air horn, because I figure that is only making things leaner without it.

It runs best with the JD tuner running fat at idle and 44 clicks on the cold air bypass. I messed with the TPS some more, but not much change really.

I thought I found the smoking gun, but I was not that fortunate.

no, I think you have found it.

you need to adjust the tps now. Also, measure the voltage first, maybe. (the throttle plate should be closing more, so the voltage will be different. get it back to around 0.680v at closed throttle)

 

[Trenchcoat85]

Keep the air horn in (aka velocity stack). but it will make you leaner, believe or not- they smooth out the airflow to 'purt near laminar flow.

 

[Trenchcoat85]

the idle bypass control will probably have to be adjusted. I think the manual is wrong on which direction to turn IIRC.

 

[durtkillon]

I want that to be true, but I tried 0.68v and it would not start hot. I got it to run and idle at 44 clicks and 0.75v and some successful hot starts, but eventually it failed to start hot. The hot start issue persists at all tps settings from 0.4 to 0.8V. I messed with just TPS settings for a couple hours today.

I found another issue on the bike that could be related. I took the time to review the non factory wiring for the after market headlight and the trail tech computer. I found the headlight was wired to the ECU diagnostic connector in front of the bike. It consists of 3 wires - red, blue and pink. The blue from the diagnostic harness was connected to the bulb ground and the red wire on the diagnostic harness was connected as power source for the low beam bulb. A third wire was connected to the power fuse via a switch for the high beam. The pink wire was snipped and tucked away. The headlight has been removed and was disconnected for several weeks now because the wiring looked poorly done.

So the headlight had power from the ecu AND the power fuse (high beam) and it was grounding through the blue wire, back at the ECU. I have no clue what that would do to the ecu or map, but I find it concerning. I'm a little bummed the previous owner cut the diagnostic connector off as well. I think it's time to send the ecu off for some testing. ZipTy has not replied back to me yet. I will fiddle more tomorrow.


Thanks again for all the help, Trenchcoat85. Your suggestion to check for leaks lead me to check to make sure the throttle plate is closing. I believe it's set correctly now.

 

[Trenchcoat85]

cool.
does the idle bypass circuit work correctly? IOW, does it affect the idle when you adjust the screw?

you are actually making some progress if you got a few hot starts.

using the diagnostic plug to power a headlight is pretty questionable, I agree. Coupled with that ham-fisted throttle stop adjuster, I would keep a jaundiced eye open for any other mickey-mouse fixes from a previous life.

re-wire that headlight ASAP; or just disconnect it for now. (the pink wire is the only one carrying any data, but it's still a screwy way to wire-in a component)

 

[Trenchcoat85]

...and what result does a higher voltage on the tps give? like 0.850v? set the idle bypass back to 34 clicks out too; we want less air.

you probably don't want to ever lower the tps voltage past 0.680v but I'm not absolutely positive.

is the MAP mounted correctly or is any air leaking by it?

we'll get everything re-adjusted once we get this current lean issue solved.

 

[durtkillon]

The cold start bypass most certainly has an effect now. It causes higher idling and is necessary to start the bike from a complete cool down.

I disconnected all afernarket stuff except the jd tuner. I did rerout it better though.

If I try anything above 0.8 v, the bike just dies immediately.

Trenchcoat85, could you snap a foto of the diagnostic connector with the wire orientation in view? I'll try to re-pin it.

The MAP does not appear to be compromised in any way. The screw does not appear to have been marred. Removing it without marring the screw would require the throttle body to be removed. When I had the tb off, I inspected everything very closel for signs of tampering.

At 34 clicks, the bike will not idle and dies.

I'll order an extra fuel line to make a pressure tester. I need to rule out the fuel system completely. Looks like a new Husky line is $41.

 

[Trenchcoat85]

Fuel line: just slip a 1/4" line over the tank outlet (clamped gently). You may not need to run the bike- but just flash the starter button a couple of times. Looks like the worthless stock line went up $10- I just made one a couple of years ago.

Idle: are you screwing it in CW all the way and then back out? I can't remember the details but the manual might have an error. OTOH, sounds like it works and may not be leaking air. Do the propane test around the tb and manifold while idling. Weird that it won't idle at all at 34 clicks, no fuel is involved. Is air leaking around the injector? Also, it should start in the summer without pulling the cold start. What's your altitude?

MAP- I think we're okay. It runs fine.

Pic- yeah I'll take one of the diagnostic plug when the temperature drops a bit. If you insulate the wire ends you'll be good.