kdx200 coolant not circulating

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kdx200 coolant not circulating

Postby BigH » 10:29 pm Jun 27 2015

Hello, my name is Hal. I,m 55 yrs old & rode mostly all dirt & motorcross bikes until i was 24. Never lost the desire to ride again. 3 years ago i purchased a ttr230 but i ride with my son & his friends. All have 250 motorcrossers. the ttr just couldn't keep up so i purchased a 2005 kdx200. I noticed that the coolant does not circulate when throttle is applied. I'm thinking bad head gasket? i noticed that the head is attached to the frame? Very unusual. Vibration maybe causes premature failure? Do they have problems with the impellor that moves the coolant? Is it direct drive? Also there is another wrinkle. When I bought it I was told it was bored 20 over. Does any one know if that would require a 200 or 220 head gasket?
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Re: kdx200 coolant not circulating

Postby ohgood » 07:15 am Jun 28 2015

can't help you with the overbore question, but a little with the coolant.

fill the bike with coolant, crack the 'burp' plug that is on top of the head. (remove fuel tank for easy access)
lay the bike over left/right a little, to make sure all the air bubbles make it to the top-o-the-head burper.
close that burper
crack the burper on top of the LEFT side radiator.
fill the right again, if you can.

kick the bike and see if you have coolant flow now. if not, pull the waterpump cover and check there. should be apparent then.

:)
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Re: kdx200 coolant not circulating

Postby bufftester » 03:49 pm Jun 29 2015

How are you checking coolant flow with the bike running? Are you losing coolant? As for the head attached to the frame that is normal for 2Ts across all manufacturers. My RMXs are that way as are the KX and KDXs. If you had a bad head gasket you'd be running poorly and loosing coolant. If you arent' loosing coolant check the water pump impeller/bearing/seals (though again, if the seals were bad you'd be loosing coolant). I have seen an impeller that the nut came loose on and it was not spinning with the shaft.
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kdx200 coolant not circulating

Postby BigH » 05:06 pm Jun 30 2015

I tried the burping procedure suggested today. I observed no air bubbles @ all. I check the flow with the bike running & cap off. There is some movement in the coolant but it is not a circulating movement. It splashes out the top. Correct me if i'm wrong but the coolant should suck down & start circulating quit clealy as it does on my sons yz250. I do not see any coolant leakage. Will check the impellor next. Do not have a gasket but could use silicone. The head does not seem too hot when i ride. i compare it to my sons yz which i know is cooling properly.
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Re: kdx200 coolant not circulating

Postby bufftester » 09:20 pm Jun 30 2015

Your cooling system is different than your son's YZ. Most MX bikes use bypass radiators where half the coolant flows through each radiator. THe KDX uses a non bypass so all the coolant flows from the bottom of the right side radiator up to the top then down the left side radiator and into the motor. The result is that when the cap is off it splashes. If you are not loosing coolant during a ride, and your oil is not milky looking, and you are not overheating then your cooling system is working fine. Don't make work where there is none.
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kdx200 coolant not circulating

Postby BigH » 11:34 pm Jun 30 2015

Thanks for the information! that helps alot! I believe it is functioning normally with the new info you just supplied me. Only other problem I am having does not idle high enough & sometimes stalls. Pain in the ass. air flow screw is 2 turns out & idle screw mostly all the way in. From all the tips i have been reading it sound like i need jetting?
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Re: kdx200 coolant not circulating

Postby fuzzy » 01:27 pm Jul 01 2015

Indeed!
'91 KDX 200 Project $300 KDX
'95 KDX 200 Project $600 KDX
'94 WR 250 Always a project
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Re: kdx200 coolant not circulating

Postby bufftester » 03:06 pm Jul 01 2015

Walk through the jetting guide and you'll be square
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kdx200 coolant not circulating

Postby BigH » 09:38 am Jul 02 2015

where can u get a fuel level tool? is there a make shift one u can use? Was told it had boyesen reeds. Have not checked the condition or if it even has them yet. Took a leap of faith & started through the procedure if nothing else to get familiar with it. compression is @ 150 which according to my manual is top of the scale. high idle is right around 1 1/2 turns. had to move needle up 1 notch to get rid of the momentary bog (good ridens). When doing straight away the result is always a oily wet plug. A couple of notes. do not know whether this is normal but the snorkel & top of the air box is not on bike. Normally the oily plug would indicate a smaller main is needed if i understand the procedure. Need fuel level tool to verify float level. will clean carb (was dirty when i took slide out to move needle). Check reeds & repack silencer. i run it @ about 42:1. i will repeat procedure if still rich will let you. Any other suggestions let me know. Thanks for the info. BigH
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Re: kdx200 coolant not circulating

Postby ohgood » 01:43 pm Jul 02 2015

BigH wrote:where can u get a fuel level tool? is there a make shift one u can use? Was told it had boyesen reeds. Have not checked the condition or if it even has them yet. Took a leap of faith & started through the procedure if nothing else to get familiar with it. compression is @ 150 which according to my manual is top of the scale. high idle is right around 1 1/2 turns. had to move needle up 1 notch to get rid of the momentary bog (good ridens). When doing straight away the result is always a oily wet plug. A couple of notes. do not know whether this is normal but the snorkel & top of the air box is not on bike. Normally the oily plug would indicate a smaller main is needed if i understand the procedure. Need fuel level tool to verify float level. will clean carb (was dirty when i took slide out to move needle). Check reeds & repack silencer. i run it @ about 42:1. i will repeat procedure if still rich will let you. Any other suggestions let me know. Thanks for the info. BigH

17mm from the surface of the carb body to the top of the float...

and just touching the tang to the float needle, but not compressing it.

you can do it with calipers, or site along anything that is 17mm
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