2018 kx250f bogging and backfiring after a few laps

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11/25/2018 5:21 PM

I have had nothing but headache with this bike, this was happening before I got my bike remapped so I can rule that out. 12 hours on bike, starts easy, runs amazing for about 4 laps, then it won’t rev up, just bogs....it was 65 degrees today, water pump working great. Right before the bogging starts it will backfire a few times if I get it close to the rev limiter, a single loud “pop”. I run half vp110 and half pump gas. Clean air filter, water pump working, I can blow thru vent on gas cap with my mouth so it’s not stopped up. If I come back to truck for 15 mins I can get a few laps of normal riding before it begins again. Ideas? I’m going to drain the tank tomorrow. It water in gas doesn’t make sense to me being it only does it after a few laps.

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11/25/2018 5:54 PM

I would begin with adjusting your tps sensor to .62v.

If that dont work id bet your coolant temp sensor is messed up. Whatever your issue is, its related to heat causing the problem. But the popping and backfiring sounds like tps.

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11/26/2018 11:57 AM

Check your fuel pump and filter.
Also do an OHMS test on the coil. It can break down when heated. When cooled it can recover and then repeat.
You may also want to look into fuel tank heat shield wrap as vapor locking can happen when the fuel gets hot in the tank.
I think your bike also has a sensor for over heating that can be going bad.
Also as already stated, the TPS is set too lean from the factory.

Paw Paw

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11/26/2018 1:13 PM
Edited Date/Time: 11/26/2018 1:15 PM

kb228 wrote:

I would begin with adjusting your tps sensor to .62v.

If that dont work id bet your coolant temp sensor is messed up. Whatever your issue is, its related to heat causing the problem. But the popping and backfiring sounds like tps.

Curious about the TPS settings, but don't know much. What is the difference between raising or lowering the TPS- does it run richer or leaner and any other points of the effect it has? PawPaw's post above also says is set to lean as standard?

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Always was an excellent rider ...... at crashing usually

Moto Aspes, you know you want one

11/26/2018 1:27 PM

The tps is what tells the computer how far open the throttle is. Thus telling it how much gas to inject into the throttle body. So what happens with most bikes from the factory is the tps voltage is telling the ecu the throttle is more closed than it actually is, and it injects less fuel causing the lean mixture. Thats what causes the popping. Higher voltage is richer.

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11/26/2018 1:38 PM

Thanks KB. Lowered it on my car hoping to get more MPG, thought it maybe was as you said but nice to know for sure.

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Always was an excellent rider ...... at crashing usually

Moto Aspes, you know you want one

11/26/2018 3:58 PM

Factory setting is normally .5 volts and what it needs is a setting of about .6-.62 volts at idle. I would also check it at WOT as I have seen several newer Kaw's that would not get the full 5 volts at WTO and that can also be an issue with the TPS. The TPS effects the fuel delivery from idle to WOT. kb228 gave you solid info above.

Paw Paw

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11/26/2018 10:02 PM

PhotoWell I took the tank off today and the filter looked pretty dirty, and the tank had debris in it, cleaned everything up, even the injectors. What do y’all think? Photo
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11/26/2018 10:05 PM

Also, I will try and set tps when I out back together, which wire is which on the tps? I have black yellow and blue. I replace the torx head with a 8mm so I can adjust on bike

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11/27/2018 3:24 AM

I think you just broke your fuel pump from removing that filter. They do NOT go back together. Trust me ive tried.

You need a new fuel pump. Since yours is apart already, order an aftermarket one from quantum.

To adjust your tps you need to have a harness that allows you to attach a volt ohm meter. You also need to connect a battery to the bike. Service manual will tell you how to hook all that up. Kawi is really good about schematics.

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11/27/2018 4:57 AM

kb228, What kind of battery is used to check tps voltage. Where do you get the harness?

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No brains, No headaches.

11/27/2018 6:43 AM

kb228 wrote:

I think you just broke your fuel pump from removing that filter. They do NOT go back together. Trust me ive tried.

You need a new fuel pump. Since yours is apart already, order an aftermarket one from quantum.

To adjust your tps you need to have a harness that allows you to attach a volt ohm meter. You also need to connect a battery to the bike. Service manual will tell you how to hook all that up. Kawi is really good about schematics.

They go back together super easy, not sure why you would think they don’t, a couple different threads on here show this process

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11/27/2018 7:53 AM

Wow those quantum pumps are cheap, at that price I’ll buy one anyways because I don’t feel like coming up short on a 100ft triple again ...

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11/27/2018 8:14 AM

kb228 wrote:

I think you just broke your fuel pump from removing that filter. They do NOT go back together. Trust me ive tried.

You need a new fuel pump. Since yours is apart already, order an aftermarket one from quantum.

To adjust your tps you need to have a harness that allows you to attach a volt ohm meter. You also need to connect a battery to the bike. Service manual will tell you how to hook all that up. Kawi is really good about schematics.

Blake_Toms wrote:

They go back together super easy, not sure why you would think they don’t, a couple different threads on here show this process

Because ive physically tried to reassemble my kx fuel pump. It does not “snap” back together at all. Got it to go back once and came back the next day and it fell back off overnight. Its the reason fuel filters arent serviceable on these pumps. Same for all but honda and ktm i think.

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11/27/2018 8:19 AM

Keith72 wrote:

kb228, What kind of battery is used to check tps voltage. Where do you get the harness?

A small 12v atv battery from walmart works just fine.

I made my harness with wire and alligator clips i got at walmart. Sauldered it all together. You can buy one from kawasaki. Some people get them from tps tool or something like that.

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11/27/2018 8:20 AM

Keith72 wrote:

kb228, What kind of battery is used to check tps voltage. Where do you get the harness?

A small 12v atv battery from walmart works just fine.

I made my harness with wire and alligator clips i got at walmart. Sauldered it all together. You can buy one from kawasaki. Some people get them from tps tool or something like that too.

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11/27/2018 8:28 AM

kb228 wrote:

I think you just broke your fuel pump from removing that filter. They do NOT go back together. Trust me ive tried.

You need a new fuel pump. Since yours is apart already, order an aftermarket one from quantum.

To adjust your tps you need to have a harness that allows you to attach a volt ohm meter. You also need to connect a battery to the bike. Service manual will tell you how to hook all that up. Kawi is really good about schematics.

Blake_Toms wrote:

They go back together super easy, not sure why you would think they don’t, a couple different threads on here show this process

kb228 wrote:

Because ive physically tried to reassemble my kx fuel pump. It does not “snap” back together at all. Got it to go back once and came back the next day and it fell back off overnight. Its the reason fuel filters arent serviceable on these pumps. Same for all but honda and ktm i think.

I heated it up carefully and squeezed it with pliers and it held, once it goes back in the housing the kinda supports it too, may ride it this weekend on that pump depending on if the new one comes in

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11/27/2018 8:31 AM

kb228 wrote:

I think you just broke your fuel pump from removing that filter. They do NOT go back together. Trust me ive tried.

You need a new fuel pump. Since yours is apart already, order an aftermarket one from quantum.

To adjust your tps you need to have a harness that allows you to attach a volt ohm meter. You also need to connect a battery to the bike. Service manual will tell you how to hook all that up. Kawi is really good about schematics.

Blake_Toms wrote:

They go back together super easy, not sure why you would think they don’t, a couple different threads on here show this process

kb228 wrote:

Because ive physically tried to reassemble my kx fuel pump. It does not “snap” back together at all. Got it to go back once and came back the next day and it fell back off overnight. Its the reason fuel filters arent serviceable on these pumps. Same for all but honda and ktm i think.

I heated it up carefully and squeezed it with pliers and it held, once it goes back in the housing the kinda supports it too, may ride it this weekend on that pump depending on if the new one comes in

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11/27/2018 4:59 PM

I use a 9volt battery and bought a 5pack of snap on 6in. wire pigtails from radio shack years ago. Hold one of the wires to one side and tap the other wire on/off to ignite the the injector. I used a syringe filled with B&G injector cleaner mated up with correct size fuel hose to purge injector both directions. Mcgiver has nothing on me haha'

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11/29/2018 9:52 PM

Twin air makes a relatively cheap tpms tool that will help you adjust it properly. Or just bring it to a kawi dealer and they can do it for you saving u time money and aggrivation. Id throw a new plug in too just to rule that out. I don't know what it is with kawi and tpms sensors, had an issue with my 2011 also. Would randomly go into this odd "limp mode". I've seen one other kawi do what you're describing...it was a 450 and turned out to be a bad fuel tank that wasnt sealing with the pump properly...kawi warrantied a new pump, tank and labor. If I were you I would take the bike back to the dealership you got it from and talk with the service manager about what's going on...it sounds like it might be something kawi would warranty. Definetely shouldn't be doing what ur describing, especially if it was doing it before u remapped it.

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