At a loss please help!

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At a loss please help!

Postby Kdxjarret » 01:20 pm Dec 28 2017

Ok..... First off I am new to dirtbikes and new to 2T but know my way around a tool box. Here is what I started with, what I have done ,and where I am at.

Bought 96KDX200
Recent top end... I have receipts
Top end done by PO and you can obviously tell it's been off recently. Compression 180psi
Air box opened up
FMH gnarly woods pipe and silencer.
Running extremely rich when I got it. Excessive smoke and spooge. Bike ran but not much power and this is important....never fouled a plug but to be fair I didn't ride it much.

What i have done....
Used jetting guide and started down the list.
Repacked silencer.
Fresh plug
Checked compression 180
Checked Kips, it wasnt working correctly due to the ball bearing on the return spring was missing. Finger nail polish mixing ball works as a replacement. Snaps back as it should and working good.
Doesn't seem to be dropping any crank case oil
Cleaned carb good inspected needles and seats.
Set float to spec and tested for seal
Went from 42P 155M to 32P 150M
Needle second from top notch
600ft above sea level and 40-50F
40:1 Amsoil Dom, 93 non eth
Fuel filter is clean, tank cleaned
Fresh air filter.
Has good spark even when hot
Reeds looked good when checked

Now.....
Bike runs great. Cranks first kick. Good power. Lofts front tire on 2nd with ease i am 205lbs. Runs great then out of the blue it fouls plug. Didn't start doing this till I changed jetting.

Thinks I noticed
Fouled plugs are wet and shiney not oily
It sometimes but not always drips fuel
Air / fuel sre w doesn't seem to really make much changes... This made it difficult to jet.
Jetting seems lean to me but it smokes a nice grey and has min spooge but does have some.

So..... Is my carb just junk?
Jet block gasket maybe?
Mainly is this something other than a carb issue?
If it's carb only i am just going to buy a new oem or maybe a lectron. Is there anything else I am missing?

Thanks in advance
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Re: At a loss please help!

Postby doctord23 » 01:49 pm Dec 28 2017

It sounds like you have been heading the right direction with the build.
Right off the bat, I would say that the pilot jet is too small and that is why the air screw has no effect.
I have never gone lower than a 40 pilot and had it run correctly.
Something is probably masking the pilot jet size issue which may indicate that carb is defective or is feeding another source of fuel such as a bad choke circuit, float level or jet block.
Hard to diagnose, but a 42 pilot should be about right for your conditions.
Still doesn't explain the plug fouling. What plug are you running?
I have maybe had one fouled plug between all of my kdx's.

Good luck.
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At a loss please help!

Postby Kdxjarret » 02:19 pm Dec 28 2017

Running B8ES plug, gone through about 8 now. I have taken the carb off so many times I could do it blind folded. I have ruled out float needle cause it looks new and perfect. Choke circuit also cause I pulled it and checked it to make sure it closes and seals properly. I just want to make positive that my issues is in the carb before I spend any more money on it. I have $900 in the bike and it came with new tires unmounted, new o ring chain in box, new sprockets in box. Plus a bunch of other goodies. I figure if it’s the carburetor I am just going to pony up and go with a new one. At this point the jet block is what I am thinking but so fed up with the POS that I want to use the current carb for target practice!
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Re: At a loss please help!

Postby david » 03:59 pm Dec 28 2017

From what you said, the float is not closing the inlet needle completely. I had to set mine to 18mm. If you turn off the fuel valve when idling, does your idle speed up immediately?


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At a loss please help!

Postby tmmyghst » 04:04 pm Dec 28 2017

I would do the jet block gasket just to eliminate it as a possibility now and in the future.
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Re: At a loss please help!

Postby raygun » 09:34 pm Dec 28 2017

I agree when it comes to the jet block gasket, easy to do and it's probably junk by now anyways. I fought similar demons, changed the jet block gasket and it changed everything, much easier to tune predictably.
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At a loss please help!

Postby SS109 » 10:49 pm Dec 28 2017

No reason to replace a carb unless it has obvious bad wear on it and especially so for what a genuine Keihin PWK carb cost ($225+). Stock float tends to be too high IMO/IME. Lower it a bit. Get a carb rebuild kit (jetsrus - $15.55) and replace the needle valve anyway. They are cheap so why not? Replace the jet block gasket (jetsrus - $4.41). Again they are cheap so do it.

I agree that the pilot jet is way too lean. Even the main seems lean to me. I ride around 2000ft and the leanest was a 38 pilot/152 main. Do you possibly have the idle speed screw too high? I have seen many have this problem when trying to sort their pilot jet. I would probably start with a 42 and then make sure the idle speed is low enough that you aren't running on the main jet/needle at all.

Lastly, have you been losing any coolant? Transmission oil? How did you clean the carb, dip/soak or just spray carb cleaner?
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At a loss please help!

Postby Kdxjarret » 12:48 pm Dec 29 2017

Thanks for the responses... I plan on ordering rebuild kit and jet block gasket today.

I haven’t seen any loss of crankcase oil. I changed it when I got the bike and have been keeping an eye on it. As far as coolant I can’t see any noticeable loss. I did wonder with the coolant line going in to top of the head if that could be an issue. Possibly a cracked head. If it was dumping coolant into cylinder I think that would be obvious. Similar to a blown head gasket.

I cleaned the carb with standard carb cleaner and compressed air. I did not soak it. I only soak carb parts not whole carbs. Been down that road before.

As soon as the parts come in I will get an update for you guys
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Re: At a loss please help!

Postby Kdxjarret » 05:20 pm Dec 29 2017

Ok.... parts are ordered. I couldn’t help myself so I pulled the jet block off and the gasket didn’t resemble a gasket at all. Needless to say I really hope this teamed with float level is the issue. Before I start doing the victory dance and passing out cigars let me get it put back together and test it. Be 10-12 days before parts are in. Thanks for all the help so far.
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Re: At a loss please help!

Postby Jason » 07:03 pm Dec 29 2017

It is an o ring of sorts.
Good luck.
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: At a loss please help!

Postby Kdxjarret » 06:32 pm Jan 02 2018

Jet block o-ring is installed and I am positive that was 1\2 my issue. Bike runs good and it's got a 42/152 instead of 32/150. Hasn't fouled a plug but didn't really get to run it very long due to its really cold here in NC at the moment.

Now....... I read every float setting guide i could find and float is set at 18mm. It's still a bit rich. Airscrew still hard to hear idle kick up to tune. I can p!ay with pedock and it instantly starts to clear up.
Float is good no holes
Float needle is sealing... Checked by blowing air
Float needle , airscrew and spring new

To be clear..... 18mm from top of float to bowl mating surface. Measured once the tab hits the float needle but doesn't press in the spring loaded rod.

What am I missing?
Should I go to 20mm?
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Re: At a loss please help!

Postby bzdang » 07:18 pm Jan 02 2018

Sounds like you're doing things right.
Might be worth checking if the left and right float tanks are at the same height (mine got twisted a bit from mis-handling and one side was too high). And if there's too much play in the float pivot (worn holes in the carb body) it could raise the fuel level or allow the tanks to shift sideways and snag in the carb body.
Last thing I can think of, is a reminder that these things take a while to heat up, even in nice autumn weather, and they run gross until they're hot enough.
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Re: At a loss please help!

Postby david » 05:43 pm Jan 08 2018

If your idle increases a little as soon as you shut off the petcock, you are still getting some fuel past the inlet needle when it should be closed.
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Re: At a loss please help!

Postby Kdxjarret » 07:16 pm Jan 09 2018

Yeah it increases from the petcock. I am going to try setting it at 19mm next. Also when I had the carb off last i was blowing air into the choke circuit with the choke off and I could hear air coming through the carb somewhere but not sure where from. The plunger looks good and choke seems to work to crank the bike. Didn't know if the choke circuit loops back it bowl when closed or not.
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Re: At a loss please help!

Postby Kdxjarret » 09:47 pm Jan 10 2018

bzdang wrote:Sounds like you're doing things right.
Might be worth checking if the left and right float tanks are at the same height (mine got twisted a bit from mis-handling and one side was too high). And if there's too much play in the float pivot (worn holes in the carb body) it could raise the fuel level or allow the tanks to shift sideways and snag in the carb body.
Last thing I can think of, is a reminder that these things take a while to heat up, even in nice autumn weather, and they run gross until they're hot enough.


I checked the float and it was a bit out of whack. After a good bit of adjustment, checking and rechecking, measuring from both sides I reassembled. I even polished the float valve seat. I set the float at 18mm and away I went. I took it out to get it warm so I could tune the airscrew. Pulled back in shop and it cut off before I could get my screw driver. Couldn’t get it to start back. Here we go again!
Pulled carb for the 100th time! Figured trash so I took it apart and cleaned every passage with torch tip wire, carb cleaner and air... put it back together. Still won’t run... pulled plug and swapped it and it fired and ran... but was short lived acted as if it was not getting fuel... it has spark but the plugs I have have all been fouled before but are clean. Frustrated I went inside for a breather.... I forgot to turn fuel off so when i returned it was pissing fuel. So.....

It has compression
It has fire but am getting more plugs tomorrow just to make sure.
Has fuel....

WTH!!! I am really at the end of my wits! I like this bike and I really want to love it but a 4t is looking better and better.

Should i check my reeds?



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Re: At a loss please help!

Postby Jason » 02:31 am Jan 11 2018

You have a 22 year old float valve / seat / floats. Something is wrong with one or more of them.

You can get a different bike, but what problems does it have?? (unless you buy brand new)
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: At a loss please help!

Postby Kdxjarret » 10:23 am Jan 11 2018

Jason wrote:You have a 22 year old float valve / seat / floats. Something is wrong with one or more of them.

You can get a different bike, but what problems does it have?? (unless you buy brand new)


Float valve is new
Float is functional ... no holes... floats
The seat looks good but hard to really tell... I was under the impression that the seats can not be replaced. Is this correct?


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Re: At a loss please help!

Postby Jason » 11:30 am Jan 11 2018

If it functions properly, then it is out of adjustment.
Thank you, Julien D for all your hard work!

PLEASE! Do not "dip" PWK Keihin carbs in Berryman's to clean them! It will damage the internal o-ring (jet block gasket).
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Re: At a loss please help!

Postby Kdxjarret » 08:46 pm Jan 12 2018

Jason wrote:If it functions properly, then it is out of adjustment.


Rechecked the float height again and increased it to 18.5mm... turned the fuel on and it hasn’t pissed yet.

I threw a fresh plug in an the bike fired up first kick. I hope to get out and ride a little this weekend if I can. I just want to see if my issues have been resolved. Keeping my fingers crossed.

Thanks to everyone for the help!


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Re: At a loss please help!

Postby Kdxjarret » 08:33 pm Jan 14 2018

Got the KDX out for a few mins this weekend and so far so good. Bike ran good but still has a bog off idle... I am assuming it’s a rich bog. I am thinking it’s a just some air screw tuning needed. Either way I am just glad to have the fuel issue resolved so I can start really learning how to dial it in. Thanks again for all the help.


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