2018 KX250F shutting down

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12/1/2018 7:18 AM
Edited Date/Time: 2/3/2019 1:27 PM

Hello guys,

I'm a beginner rider, I don't rip my bike hard.
My bike fires with 2 kicks when cold. It can idle for 2 minutes and it will shut down by itself and then It won't let me kick start without choke. After riding for a couple min' it wants to shut down when reaching low rpm and won't respond to opening throttle and have a delay, then it will respond and give power. But something is definitely weird.

I gave a friend a small test lap and he only felt it once.

When the bike is hot, it will start with 1 small kick, when I put into 1st while clutch is pulled all the way in, I rev it a little and it shuts down without releasing the clutch. I can ride it if I throw the clutch a bit and rev higher, but I never had this issue before.

also while riding, it randomly wants to shut down, like it's choking or not getting fuel (usually happens in low rpm). If I rev it, it goes back to normal. I've had this happen even in 5th gear going downhill without throttle, getting to the end of the downhill with low rpm the bike losing power and won't respond to throttle opening and shutting down. I can kick it and continue to ride but it will happen again randomly.

The first time I noticed something is wrong was when I went wide open in 5th gear and felt for a split second like there was a cut in fuel / air and then it kept going as normal. But since that day, it's been worse each time. Not sure what's the problem.

It's a brand new 2018 KX250F from the dealer. I've done +30 hour. Never done valve clearance yet. Will do next week, but don't know if it's related, because the bike starts with first kick, but acting weird when riding.


EDIT: The issue is the air temp sensor.
Bad wires / not sitting properly / sensor wobbles.

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12/1/2018 7:35 AM

I think your valves are fine.

Make sure your idle is at 1800-2000 rpm. If its too low youll have issues. Theres a knob on the throttle body, turn it and it will change your idle speed. Its the “choke” knob you were referring to.

Throw in a new spark plug.

Check all your electrical connections. Clean them with electrical contact cleaner and use some dielectric grease on the plugs.

Sounds like a fuel pump or fuel injector issue to me though.

Sometimes when the temp sensors are broken it can cause that type of issue too.

If youre new, try to find an experienced mechanic to help you. Start with the cheapest stuff first. Fuel pumps are $350 and injectors are around $100. Dont want to see you throw money down the drain.

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12/1/2018 8:35 AM

Change TPS setting from .5 v to .62 v.
Try not to log the engine down in 5 th gear when it needs to be in 3rd or 4th gear.

Paw Paw

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12/1/2018 9:33 AM
Edited Date/Time: 12/1/2018 9:35 AM

Paw Paw 271 wrote:

Change TPS setting from .5 v to .62 v.
Try not to log the engine down in 5 th gear when it needs to be in 3rd or 4th gear.

...more

I was going fast in 5th downhill, if I would downshift it would engine brake me.

If it's the TPS, how come this issue only started 3 engine hours ago?

Why does the bike shut down when putting in 1st with clutch in and rev a little without releasing the clutch?

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12/1/2018 1:21 PM

TPS can get knocked out of spec pretty easily. There’s only one Torx head bolt and even when tight the sensor can be rotated. It’s quite sensitive. The Yamaha’s have two bolts holding the TPS & I think that’s a better design. There have been several Kx250f owners having similar fuel delivery issues. It’s usually one of two things, or both; a dirty fuel pump filter or ECU setting is off. A quantum fuel pump replacement is $70, FYI and just as good as OEM I’ve found. Also, the bike feels “snappiest” when the TPS is set at .62 - .63 I’ve found. Most of the KX250F’s I’ve worked on and owned were set at the .55-.56 range, and it makes quite a difference when it’s dialed to .62.

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12/1/2018 2:27 PM
Edited Date/Time: 12/1/2018 2:57 PM

kb228 wrote:

I think your valves are fine.

Make sure your idle is at 1800-2000 rpm. If its too low youll have issues. Theres a knob on ...more

The bike sounds the same as the day I purchased it, and everything feels the same besides the issue stated in the topic.
Just something "clogged" or I don't know... riding slow in 1st or second gear and the engine wanted to shut down, but doesn't sound like the normal shut down when you don't pull the clutch in time, it's more like getting weak and dying. But it didn't die because I gave it more throttle and it responded with a delay.

photos of my current plug:

Photo

Photo

a video showing my friend the sound (maybe it can help you hear something).



Do I need to change only the idle TPS for 0.62 volts or also the the full throttle opening volts? What about input voltage?

Can my issue be related to a faulty water pump?
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12/1/2018 3:00 PM

Put in a new plug and check your tps voltage. You set it at closed throttle. Your problem doesnt seem as bad as i had in mind after watching your video. A waterpump wont cause issues like that. A faulty water temp senser might, but i dont think thats your issue.

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12/1/2018 3:09 PM
Edited Date/Time: 12/1/2018 4:30 PM

kb228 wrote:

Put in a new plug and check your tps voltage. You set it at closed throttle. Your problem doesnt seem as bad as i had in mind ...more

Thanks for your help!
I will do a better video tomorrow, hope it's just a simple solution...
Can this happen if I wash the bike with a too strong water stream?

This video shows something similar to what I'm experiencing but mine is not as bad.

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12/1/2018 4:41 PM

The sensors can be thrown off from vibration. Theyre off from the factory too. You can change it by applying pressure to it with your finger. Its just something that happens. Id say its the most common issue i see on here. Happens to seemingly every model.

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12/1/2018 4:45 PM

Not sure how I can change it by applying pressure to it with my fingers and how accurate it can be.
Should I just bring the bike to the dealer and have them fix it? (maybe that's not the main issue? don't know).

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12/1/2018 7:20 PM

Titan777 wrote:

Not sure how I can change it by applying pressure to it with my fingers and how accurate it can be.
Should I just bring the ...more

What i meant is that sensor is very touchy. If you have a multimeter hooked up, you can touch the sensor and the voltage will change. If you do not know what you are doing, yes take it to a mechanic who does. Try to find one who isnt a dealer. The kawi dealer here charges $85 an hour or a $100 diagnosis fee.

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12/2/2018 3:28 PM
Edited Date/Time: 12/2/2018 3:30 PM

Titan777 wrote:

Not sure how I can change it by applying pressure to it with my fingers and how accurate it can be.
Should I just bring the ...more

kb228 wrote:

What i meant is that sensor is very touchy. If you have a multimeter hooked up, you can touch the sensor and the voltage will ...more

Today I tried to start the bike and everything went normal, even rode a bit in the dealer parking lot. We thought nothing is wrong, since I changed the air filter and cleaned the plug.

But when I came back later to pick up the bike (they can't fix the bike until Wednesday), suddenly after starting and trying to ride, 1st gear shuts the bike off when revving just a little bit without clutch release. Even the mechanic tried to ride and the bike would shut down once he revs and tries to release the clutch in gear. Said something it wrong (obviously).

It's like in low rpm the bike wants to die but if I pass that with aggressive throttle, it's kind of back to normal. But I did notice lack of power, in 5th gear the bike felt weak and sounded too screamy in about 60% throttle. Felt like it's 3rd gear, didn't pull hard and the speed wasn't high for normal 5th gear.

Still think it's the TPS sensor?
Can they know if one of the sensors is bad by attaching the bike to the Kawi diagnosis computer program? (that's what they said, that it's all computers and sensors these days and it will tell where the issue is).

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12/2/2018 4:35 PM

Yes they can hook it up and take a look. Try a NEW spark plug. Not a cleaned one.

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12/2/2018 6:00 PM

kb228 wrote:

Yes they can hook it up and take a look. Try a NEW spark plug. Not a cleaned one.

Can a spark plug make all these problems with rpm and "choking" feel / shutting down engine / overall low performance?

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12/2/2018 7:38 PM

I had to put a fuel pump in my 2018 kx250f the other day, somehow I got trash in the tank and it sucked it up, but mine was not doing exactly this, it was just bogging when the bike got hot

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12/2/2018 8:16 PM

Blake_Toms wrote:

I had to put a fuel pump in my 2018 kx250f the other day, somehow I got trash in the tank and it sucked it up, but mine was ...more

Did you put an OEM pump?

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12/3/2018 1:20 AM

If you need a new pump, get one from quantum. They sell replacement pumps with serviceable fuel filters for a really good deal. OEM ones are $350 with rocky mountains discount.

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12/3/2018 7:52 AM

kb228 wrote:

If you need a new pump, get one from quantum. They sell replacement pumps with serviceable fuel filters for a really good ...more

I read it doesn't fit 100% inside the OEM housing, not sure though...
Any test of the flow vs OEM ?

You still think my issue is electrical / sensors? Or might just be a bad spark plug / Fuel pump?

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12/3/2018 8:15 AM

kb228 wrote:

If you need a new pump, get one from quantum. They sell replacement pumps with serviceable fuel filters for a really good ...more

Titan777 wrote:

I read it doesn't fit 100% inside the OEM housing, not sure though...
Any test of the flow vs OEM ?

You still think my issue ...more

I know for a fact that it does because one is in my kx450 now and it works perfectly fine.

Honestly man it could be anything. Starting with your tps is the right move.

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12/3/2018 8:49 AM
Edited Date/Time: 12/3/2018 8:49 AM

kb228 wrote:

If you need a new pump, get one from quantum. They sell replacement pumps with serviceable fuel filters for a really good ...more

Titan777 wrote:

I read it doesn't fit 100% inside the OEM housing, not sure though...
Any test of the flow vs OEM ?

You still think my issue ...more

kb228 wrote:

I know for a fact that it does because one is in my kx450 now and it works perfectly fine.

Honestly man it could be ...more

This?
https://www.amazon.com/HFP-397-2009-2010-Kawasaki-ER-6N-ER6N-ER650/dp/B016LE5T9A

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12/3/2018 9:12 AM

Yes sir thats the one

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12/3/2018 3:44 PM

kb228 wrote:

Yes sir thats the one

Thank you! (:

When do I need to replace this connecting muffler gasket?

Photo

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12/3/2018 3:46 PM

kb228 wrote:

Yes sir thats the one

Titan777 wrote:

Thank you! (:

When do I need to replace this connecting muffler gasket?

Photo

Idk when it starts leaking i guess. Never had to replace that

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12/4/2018 9:39 AM

Blake_Toms wrote:

I had to put a fuel pump in my 2018 kx250f the other day, somehow I got trash in the tank and it sucked it up, but mine was ...more

Titan777 wrote:

Did you put an OEM pump?

I used quantum, fit perfect

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12/5/2018 6:18 PM
Edited Date/Time: 12/5/2018 6:36 PM

kb228 wrote:

Yes they can hook it up and take a look. Try a NEW spark plug. Not a cleaned one.

By the way, can this be a clutch issue?

In idle, shifting from neutral to 1st with clutch pulled, everything is good, but once revving just a little bit without clutch release - the bike shuts off. Doesn't always happen.
Another weird thing, when going downhill in 2nd, I pulled the clutch all in to see if the bike will shut off and it did. When I released the clutch it started (still going downhill).

Maybe my idle is too low?
With choke it won't die but the overall performance is weak. 5th gear feels like 3rd \ 4th. Revving it didn't give much more power.

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12/5/2018 10:00 PM

Is the bike bone stock? Check your idle, u can typically do that by feel and sound. Check your tpms sensor if the bike is already at the dealership it's very easy for them to check/adjust with the software, plus any codes your bike has will be displayed. Not gonna hurt to slap a fresh plug in....they're $10. Next id check the pump and filter. If it was me id do it in that order too, with the exception of the plug. Always try the easy and cheap things first. But like it's been discussed in other forum topics smart money is on tpms, don't know what it is with kawi and those things.

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12/6/2018 9:02 AM

cowasocki205 wrote:

Is the bike bone stock? Check your idle, u can typically do that by feel and sound. Check your tpms sensor if the bike is ...more

Yes, it's stock. I think the idle rpm is ok. I replaced a new plug an hour ago and tried to see if something has changed but still the same issue, the bike fires in 2 kicks but the power delivery is weird, has a delay and burst of power, like it's choking and releasing... as if you would stop a water hose for a moment and let go. Feels choked and snappy.... Also I felt like it wants to shut off but if I put more throttle it doesn't shutdown. (was just riding in the parking lot 1st \ 2nd gear).

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12/6/2018 7:21 PM

The dealer keeps telling me tomorrow they will get the updated Kawasaki software and it's almost been a week.
Can a honda or KTM dealer diagnose my bike or only a Kawi computer can? I'm sick of waiting and not riding.

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12/6/2018 7:46 PM

If you have a service manual for the bike and the correct sub harness to connect to your diagnostic plug and then to a battery you can see if it spits out any codes. Instead of having everything displayed on a laptop you'll basically decode a series of flashes that your efi light emits. I've never done it like that, just the laptop setup but it can be done and the service manual should walk you through it.

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12/7/2018 6:18 AM

cowasocki205 wrote:

If you have a service manual for the bike and the correct sub harness to connect to your diagnostic plug and then to a battery ...more

Do I need to buy an optional part? (Power supply harness)

Photo

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