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Discussion Starter #1
Hey guys,

I am really stumped at what has been going on with my 08 kfx 450r. I have had numerous people look at my quad including a kawi mechanics. My quad starts up great when its cold without any problems, It is not lacking any power and feels great when i ride. When i come off the track and shut it off and try and start it up again it will continue to turn over without starting unless i get lucky or let it cool down. I have checked my valve clearance and i am at .005 on my intake and .008 on my exhaust at top dead center. I replaced my decompression spring with the Factory oem part assuming it may have gotten weak. I check and adjusted my tps sensor between .62 & .64 vcd output. I have checked my battery and im getting 13.8 volts when running from my stator. When i spoke with the kawi mechanic he said even though im getting the correct reading on my tps it is most likely the cause and kawi's are know for bad tps sensors. I ended up going out and buying a new throttle body w/ injector and tps sensor. I double checked my output voltage and adjusted it to .63vdc ( Recommendation from the kawi mechanic Because i have the pcIII ) I had an extra ecu so i changed that out to see if that was the issue. It was not. this weekend i ran my quad at the track and got it nice and hot when i came off the track i tryed taking the pcIII out of the equation and i pluged it back into my stock ecu to see if that was causing the problem. After everything i have done i still cannot figure out the problem. The mechanic i was working with recommended me to get the power commander v with auto tune but its hard for me to justify buying another part that may help my problem when i know other people who race the kfx without the pcv and have no issues. Any advice would be great!
 

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I had the same problem and mine ended up being the TPS.
I already have a PCV so I just hooked up to my laptop to read the TPS and adjusted it until I was in spec range.
Seems like anything that you add that takes any electronic power requires a slight adjustment to the TPS.
 

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Hey guys,

I am really stumped at what has been going on with my 08 kfx 450r. I have had numerous people look at my quad including a kawi mechanics. My quad starts up great when its cold without any problems, It is not lacking any power and feels great when i ride. When i come off the track and shut it off and try and start it up again it will continue to turn over without starting unless i get lucky or let it cool down. I have checked my valve clearance and i am at .005 on my intake and .008 on my exhaust at top dead center. I replaced my decompression spring with the Factory oem part assuming it may have gotten weak. I check and adjusted my tps sensor between .62 & .64 vcd output. I have checked my battery and im getting 13.8 volts when running from my stator. When i spoke with the kawi mechanic he said even though im getting the correct reading on my tps it is most likely the cause and kawi's are know for bad tps sensors. I ended up going out and buying a new throttle body w/ injector and tps sensor. I double checked my output voltage and adjusted it to .63vdc ( Recommendation from the kawi mechanic Because i have the pcIII ) I had an extra ecu so i changed that out to see if that was the issue. It was not. this weekend i ran my quad at the track and got it nice and hot when i came off the track i tryed taking the pcIII out of the equation and i pluged it back into my stock ecu to see if that was causing the problem. After everything i have done i still cannot figure out the problem. The mechanic i was working with recommended me to get the power commander v with auto tune but its hard for me to justify buying another part that may help my problem when i know other people who race the kfx without the pcv and have no issues. Any advice would be great!
First start off by putting in a new spark plug NGK CPR8EB-9

valve clearance measurements
(intake 0.10mm~0.15mm) or (0.0039~0.0059 in)
(Exhaust 0.17mm~0.22mm) or (0.0067~0.0087 in)

Is your intake tube stock....???

If so, disconnect your PCIII and try it without it hooked up...

You don't need a fuel controller unless you upgrade your intake like FCI, fuelATV or velocity...(more air=more fuel)

If running a upgraded intake...try a different map...!!!

What octane fuel are you using, stock compression 12:1 needs no higher than 91 octane, if your Octane is higher than 91 your ending up with fuel residue from a incomplete burn off ...
 

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I have the same problem, took it in to get it looked at and the guy adjusted my tps and it ran great for about 2weeks, then just today the same thing happened. Back in the shop. It's frustrating
 

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i just bought a 08 kfx im having the same problem it is all stock and the owner was running c12 racefuel could that be the cause
thanks
 

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i just bought a 08 kfx im having the same problem it is all stock and the owner was running c12 racefuel could that be the cause
thanks
Yes...!! Higher octane fuel will cause carbon build up because of incomplete fuel burn off causing fuel residue left for the next combustion stroke...

A compression test will verify if it's your problem...

Check your throttle positioning sensor/TPS 0.58~0.62 DCV @ close idle set at 1800 RPMs...

Check your valve clearance...valve clearance measurements
(intake 0.10mm~0.15mm) or (0.0039~0.0059 in)
(Exhaust 0.17mm~0.22mm) or (0.0067~0.0087 in)

Read this thread to help you...http://www.kfx450hq.com/forums/impo...ve-cover-gasket-plug-o-ring-decompressor.html


If your need a service manual PM me with your Email address file size 10 MB...???
 

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Discussion Starter #7
Hey dust devil, Yes i have the FCI in my quad with a k&n filter. I have a vertex high compression in it. I have a couple different maps i have tried in my quad and yes my valve clearances are in spec. I talked to a local company who comes to all of our races and they told me about unpluging my pc3 and try starting it. It didnt change it at all. Im beginning to think im just running my quad way to hot with how much i have done to my motor and i have not put in a oil cooler and im running my stock radatior. ive tryed everything i feel like... does anyone have any good maps? i have looked on all the fourms and cant find anything really close
 

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Could be a temp sensor bad throwing too much fuel to it when hot.
 

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Mine has had this problem twice.. First time I adjusted the tps and it seemed to fix the problem, but two weeks later it happened again. Turned out that my valve clearance was off and that was causing the problem. Anyone thats having this problem I would check tps and valve clearance and between those two it should solve the problem.
 

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Could be a temp sensor bad throwing too much fuel to it when hot.
Yes it can be that. Can also be the air temp sensor from heat soak off the exhaust after sitting.

Also another thing nobody said....

Electrical stuff hates heat and your ignition is the thing that hates it most.

I would have a spare plug on hand and when it does it, yank the tank right quick, pull your plug wire, pop the spare plug in it, ground to the frame and bump the starter over to see how the spark looks.

Be prepared for a shock though.

On second thought, go to advance auto and get a spark tester with the ground clamp that will hook to your frame. I've been shocked by it before and was fine. But I have been told that though rare it could get you hurt.

Another cool thing to do is get it real hot right near dark and pull it in a dark shop or basement. Do the same and watch for arcs.

I'd say you have a coil or plug cap going south, or maybe a wire rubbed or loose inside at the coil or plug cap end.
 

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Hey dust devil, Yes i have the FCI in my quad with a k&n filter. I have a vertex high compression in it. I have a couple different maps i have tried in my quad and yes my valve clearances are in spec. I talked to a local company who comes to all of our races and they told me about unpluging my pc3 and try starting it. It didnt change it at all. Im beginning to think im just running my quad way to hot with how much i have done to my motor and i have not put in a oil cooler and im running my stock radatior. ive tryed everything i feel like... does anyone have any good maps? i have looked on all the fourms and cant find anything really close
I'm running the Dynatek DRSP-1 controller & DFS ignition so I can't help you with a PCIII map, But they're many here that can..!!!

Start a New thread requesting a PCIII map for your mods...

Check your water pump impeller for wear and scale & calcium deposits, and working properly...???

How high of compression is your piston..???

What octane are you running...

Is your fan running both speeds low/high...??? 190 degrees low speed, 210 high speed kicks on...

You can put a switch on your fan, to run all the time or normally...???

What kind of 50/50 coolant are you running, and have you tried water wetter additive Red Line Synthetic Oil 80204 : Red Line Water Wetter® - 12 Oz.

or switch to engine ice only..Engine Ice Hi-Performance Coolant - Home
 

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Discussion Starter #12
thanks for the advice guys, Ill be working on it all day tomorrow so ill take a look at the sensors and ohm them out according to the repair manual. Ill also check the spark, i know i had issues in the past with the porcelain cracked and i had intermitten spark due to it maybe i got another bad plug. Ill test it and let you know how it goes
 

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thanks for the advice guys, Ill be working on it all day tomorrow so ill take a look at the sensors and ohm them out according to the repair manual. Ill also check the spark, i know i had issues in the past with the porcelain cracked and i had intermitten spark due to it maybe i got another bad plug. Ill test it and let you know how it goes
A few causes of motor's overheating...

Can you do a compression test, because if you have a build up of carbon on the piston will also cause the motor to over heat...

Water pump not working properly...

Radiator clogged or faulty cap...

Changed the coolant without burping the air out...

Fan not coming on...

Improper fuel octane or blend...leaded or unleaded, oxygenated or non oxygenated...

Improper fuel mixture, too lean...
 

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Dust Devil mentioned it, and I've found it very important. Set the idle speed to 1800rpm. Everyone concentrates on the TPS, but it's the combo of both that determines the hands-off starting mixture.

Easy starting when cold and hard starting when hot is often a too rich mixture. Try leaning out your PC at the low end.

Test for vapor lock by plumbing a pressure gauge between the fuel pump and the throttle body. The factory manual has the pressure specs, you can confirm you have steady pressure during your restart.

I think it's unlikely to be a bad electrical component, or you would likely see a failure while you are riding, not just on a hot restart.
 
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