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Discussion Starter #1
ok guys im in a pickle lol after months of talking my friend into buying a quad he finally goes for it and picks up a '05 kfx 400 claiming to have the bore kit to a 440 and a slip on exhaust. i believe that's all for $1800.. runs like a champ, i drive a 250 (ill leave out the model lol) and i say it it runs great def has more power than mine. ....but its overheating and to the point where it is boiling occasionally, mainly when hes nailing it or donuts or getting unstuck. order of approached

1) i checked for air leaks (never seen so much air crap on a quad) - no change

2) changed thermostat - no change

3) tried diff coolant started with ice i think, it was switched to the green stuff 50/50 - no change

4) changed head gasket- inspected cams n lifters, didnt mic the cam but the lifters wernt concaved. timing chain and gears look great. set the timing to i believe was ex 2 up intake 3 up on tdc comp :pissed: - NO CHANGE


what am i missing? can the water pump be jacked? or should i retard/advance the timing? but like i said aside from overheating it shows no problems starts right up runs flawless and has never shut down

appreciate any help i can get, all the threads i look at have other issues that can be causing problems
 

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Definitely pull the water pump and check it. Mine was missing all the fins on the impeller. Make sure it doesn't still have the Magnesium cover either.
 

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Where is the Thermostat located on 05 KFX 400? I thought they just had sensors.
 

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The radiator isn't full of crap is it? That will definitely cause heating problems. I would take it off and clean it real good even if it looks good. In addition to checking everything else.
 

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Yikes. If you found lifters, you definitely have an issue....
What do you mean by up 2 and up 3? Cam timing needs to be PRECISE.
Is it running lean? What jetting/carb?
 

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Discussion Starter #7
thermostat is on side of jug under water neck . the radiator is clean inside and out. and yes i would imagine there (hyd) lifters or the cam directly hits the valves which i doubt. im going there now to pull the water pump. and im not sure about the carb but as i said before it runs perfect its quick and responsive no bogging or smoking it just gets hot. as for the timing .... the gears are numbered every 90deg 1 2 3 ex is set #1 to gasket 2 up intake is set #3 up thats how i read it on these forums and it runs like it did perfect but hot. if it was a car id think valves need lashed but idk thats why im asking you kawasaki peeps
 

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Could you take a picture of where the thermostat is . I have a 2005 KFX 400 and even changed the radiator out to a new one and had the front plastics off and never saw a thermostat. I have seen them on my 2 KFX 700s. but not on the 400
 

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It's a DOHC the cams are directly over the valves...shims to set lash, and the valves get tighter as they age which leads to difficulty starting if they get too far out of spec. I wouldn't dismiss jetting, it can be close but a little lean and make it run hot, especially a big bore. Sounds like you've covered the bases as far as the cooling system goes.
What exhaust? The stock head pipe was too small even for the stock motor.
 

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Discussion Starter #10
Just follow the top rad hose to the motor its in the water neck on the head jug. It may not be in it sometimes they run them without it.

As for the pipe I'm not sure . is there a way to tell if its stock
 

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Yes - exhaust pressure can lead to higher temps in the head. So can lean jetting.
Does it cackle or back fire when you let off the throttle?
 

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Discussion Starter #13
No piping no backfireing were waiting for a clutch cover gasket to check the water pump he's pretty sad about the cost of pipes so were trying every option first. I appreciate everyone's help so far its getting pretty tragic
 

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I used to own a moded 400... If you have lean jetting it doesnt always backfire... go open up your carb and see where your jets are at. go invest in inline temp gauge... Trail tech sells one for 30$ called a TTO gauge.

check make sure your over flow isnt filling up and spewing out. *warped head isnt uncomon

cam timing is extremely important.. not something to just throw together and assume its ok.


and definitely make sure you got the magnesium cover changed / update!!!
 

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Just re-read the OP -- and had another question - is the fan coming on? Sounds like its all low speed situations where its overheating. The fan is supposed to kick on @ 190º (I think)
 

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Discussion Starter #16
so what after seems like forever the clutch plate gasket came in so we could peek at the water pump impeller. first i want to thank the guys who wrote the manual for leaving out the part about the two screws from behind the clutch plate cover going into the water pump cover.. we pried and beat and had a hell of a time lol but then we seen the screws and it came right off. smh

but anyway we pull it apart and the impeller has sepperated from the shaft - so this must be the problem right??? ha ha ha nehh he buys a full metal $60 impeller we put it together and low and behold its still boiling little to no differance

and, if i havnt stated before it is only doing it in the deep woods in and out up and down not even leaving 3rd, on straight away's its good he went back and forth hallin balls on a 1/4 mile stretch about 8 times it was maybe half inch over the F - he stopped fan popped on 30 seconds it was good. back into the woods and it over heated in 5 min. hes about to sell it he dont want to spend $400 on pipes and not have it fix it he already has probably close to $1000 into his $1800 quad were all super bummed cause hes one of my only 2 riding buddies, the other guys yz250 runs like a turd so i need to jump on a forum for him to. sad thing is i know this stuff and cant figure it out. ohhhh i love my XXXXX lol but im not liquid cooled


so in short--- aside from exauhst --- is there anything else i may have missed or can try?
 

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Discussion Starter #17
sandman yes fan works great on and off when i assume it should be and even when its boiling the temp light has only came on one time. briefly
 

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It's not the pipe; it doesn't get hot when running at high throttle settings.
I'd say jetting, and not the main jet. It's probably lean in the mid-range, and needs the needle set higher.
 

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Discussion Starter #19
As in the throttle pin? I've been putting off tearing apart the carb. Its the one that sets its self 35 I believe. And it has all the crap hooked to it. I was going to clean it when we did head gasket and set the idle air screw it looked clean and its self setting so I didn't screw with it
 

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As in the throttle pin? I've been putting off tearing apart the carb. Its the one that sets its self 35 I believe. And it has all the crap hooked to it. I was going to clean it when we did head gasket and set the idle air screw it looked clean and its self setting so I didn't screw with it
There's a throttle slide in the carb, and a needle through the slide that controls the midrange. The needle height should be adjustable with tiny circlip; usually there are 5 notches. Move the clip down lower on the needle to make it richer.
 
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