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Hey my name is Andy and I recently bought a 08 kfx 450r and it has either a wiring issue or something because it will run fine one minute and the next minute it cuts out and pops and has no power and then it will start dying out. I dont know much about wiring but it has a new battery and I have checked voltage on it. I know when I unplug the coolant temp sensor it gets worse so idk if that's the issue. Dont want to dump a bunch of money into parts it dont need. Can anyone help please
 

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I'm not the guy with all the answers but there are a couple here that do. It goes to a default setting when u unplug the coolant temp sensor and it will run worse.

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It’s tough to diagnose the FI at times

Ground the DFI circuit and see if any codes pop up.

Could be a bad coil, failing fuel pump/relay or water temp sensor
 

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I've completely reconstructed my kfx. The main wire harness, every sensor, ecu, and every bearing and bushing. Theres a lot of wires but it's not as bad as you think it is.

Are you mechanically inclined?
If you have a manual and tools, I will give u a list of things to check.

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If I had to guess... I'd go straight for the vehicle down sensor. It's under your front plastic. If your sitting on the bike it's almost dead center in front of the handlebars. It will be a 2" rectangular black box with 3 wires going in to it.
It needs to be in the correct position all of the time. I bet it's not mounted properly or it's broken and loose, and it bounces around and tries to shut you bike down

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Hey my name is Andy and I recently bought a 08 kfx 450r and it has either a wiring issue or something because it will run fine one minute and the next minute it cuts out and pops and has no power and then it will start dying out. I dont know much about wiring but it has a new battery and I have checked voltage on it. I know when I unplug the coolant temp sensor it gets worse so idk if that's the issue. Dont want to dump a bunch of money into parts it dont need. Can anyone help please
Welcome to the Forum...!!

Cutting out & popping is a very lean air/fuel mixture usually low fuel pressure... common is a clogged fuel pump strainer...

Is your motor all stock or with mods...List the mods if yes..?

Is your ECU stock or Procom...?

If the ECU is stock...Can you run the self diagnostic to point you in the right direction..?? see picture below...

Self diagnostic ORANGE wire is under the hood in a black pouch...Ground it to the frame...!
http://www.frewracing.com/users/boys/Data/InfoFiles/kfx450r/dfidiagnostics.pdf?20190827082957
 

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Discussion Starter #7
It is completely stock except power core 4 exhaust. I checked for codes and got nothing. I have messed with the down sensor some too. Even checked all the wiring for damages. I have a manual that I downloaded on my phone and am mechanically inclined. Haven't checked the screen on the fuel pump tho. It did sit for about 10 months. So that could be the issue. Not sure if it matters what grade of gas to run. Someone said I should run 91 but I put 87 in it. I have a volt meter or whatever it's called. Lol dont know much about wiring. Couldn't figure out how to test the down sensor but I thought it cut off the fuel and I know the fuel pump is working for sure.
 

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It is completely stock except power core 4 exhaust. I checked for codes and got nothing. I have messed with the down sensor some too. Even checked all the wiring for damages. I have a manual that I downloaded on my phone and am mechanically inclined. Haven't checked the screen on the fuel pump tho. It did sit for about 10 months. So that could be the issue. Not sure if it matters what grade of gas to run. Someone said I should run 91 but I put 87 in it. I have a volt meter or whatever it's called. Lol dont know much about wiring. Couldn't figure out how to test the down sensor but I thought it cut off the fuel and I know the fuel pump is working for sure.
When it sat for 10 months was there fuel in it & did you drain it, then filled it with fresh gas...??

How to clean the fuel pump... https://www.kfx450hq.com/forums/engine-efi-drivetrain/13807-how-clean-fuel-pump-2.html

Recommended 91 octane for the KFX stock 12:1 piston compression...!

To test the vehicle down sensor output voltage...see picture below...
 

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Discussion Starter #9
Ya I did change the gas but the guy I got it from did not and had been trying to get it to run. He got it from his brother that passed away. I will clean the fuel pump as soon as I get a day off and test the down sensor. Thank you all for being extremely helpful.
 

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Also does anyone know what is good and bad as far as psi numbers if I do a compression check
Sure...!

Hold the throttle wide open and crank the engine with the
electric starter several times. When the gauge stops ring,
stop cranking and read the gauge.

Cylinder Compression
Service Range:49.0∼ 81.8 psi) @900 r/min (rpm)

New motor the compression should read around 65~75psi...
 

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Can you give me a little better idea of what its actually doing when it cuts out and comes back?
I mean is it always in the same place in the rpm range?
Does it die every time it starts to cut out or does it stabilize after the bike stops moving, or rpms lower?
I'm looking for a pattern



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Discussion Starter #14
Only at high or high mid rpm. Only died out the one time when I tried to pull out and was half throttle and then it wouldnt start back for 10 minutes. Then it wouldnt idle so I just left it until next day and then it would idle fine but still cutting out the same
 

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Ok so I took the fuel pump apart and the screen is too far gone and falling apart. So where can I get a new one. On that link someone sent me on how to do it. It said something about a car part or a Suzuki part. Pretty sure this in the issue
 

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Discussion Starter #17
Ok so I put it back together without the screen after i cleaned the tank and put fresh 91 just to see if it was still doing it. It is. I just dont understand what's going on. I also found out that it will start without the rollover sensor. Wont idle and still cuts out but will run just the same
 

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Ok so I put it back together without the screen after i cleaned the tank and put fresh 91 just to see if it was still doing it. It is. I just dont understand what's going on. I also found out that it will start without the rollover sensor. Wont idle and still cuts out but will run just the same
You'll need to upload a video to a video platform like Youtube then share the link to view it...!!!

First...All sensors have to be connected & functioning correctly...!!

Second... Make sure the throttle cable has a little slack to prevent the throttle positioning sensor from bouncing causing an DFI error code...!!

Test the output voltage of the vehicle down sensor...see picture below. or this to eliminate it.. https://www.ebay.com/itm/KMS-Tip-Over-Switch-Eliminator-Kit-Kawasaki-KFX450R-KFX-450R-For-Fuel-Pump-ECU/192529855526?hash=item2cd3ac7426:g:R9gAAOSwEnZa63KQ:sc:USPSFirstClass!86404!US!-1

Replace the fuel pump & strainer...fuel pumps start to fail around full throttle and gets worse...https://www.ebay.com/itm/INTANK-FUEL-PUMP-FITS-KAWASAKI-KFX450R-KSF450-2008-2009-2010-2011-2012-2013-2014/291100258535?hash=item43c6ed70e7:g:OGUAAOSwu1tdXrWJ:sc:USPSFirstClass!86404!US!-1

And check your valve clearance...

Valve Clearance: between cam and valve lifter
Standard:
Exhaust 0.17 ∼ 0.22 mm (0.0067 ∼ 0.0087 in.) Ideal is 0.21mm
Inlet 0.10 ∼ 0.15 mm (0.0039 ∼ 0.0059 in.) Ideal is 0.14mm
 

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If there is a person that can help you get your bike running dust devil is it! I know that seems like a lot of stuff to do but knocking them out one by one is how your going to figure it out. I agree completely about the video because I cant get a good grasp on exactly what's going on. I think it sounds like a fuel issue though.

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