87 KDX 200 Bogging @ half throttle

Discussion specific to the various air-cooled KDX models sold in the USA
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

Hey guys, new rider here, I got a question about my KDX 200 I recently picked up. I don't know a ton about these bikes, so I figured I'd ask for a little advice.

My bike starts up great and sounds good, when I put it into gear and start moving everything is smooth, but as I get to half throttle to full throttle the bike starts to bog and doesn't speed up anymore, it also makes what sounds like a shuddering noise, as if it's trying to speed up but something is preventing it. Any idea what is causing this?

I know this is probably worded poorly but I'm not sure how to explain the issue very well. Any advice is welcome though, thanks!
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Re: 87 KDX 200 Bogging @ half throttle

Post by KDXGarage »

Welcome to kdxrider. It could be a few things, especially since you just got it and don't know the history.

clogged exhaust?
carburetor issue?
air filter OK?
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

Thanks for the response, I know it's hard saying what's wrong with it since the previous owner didn't share much of the history. But from what I do know the bike was his wifes fathers and was in the family for years, it started up and ran great, and then they put it in storage for 3 years after he passed and didn't touch it. I've went through the carb and everything seems fine, I haven't got a chance to take the exhaust off and check if it's clean, would that cause an issue like I'm having though?
And also there was no air filter in the bike when I got it, the previous owner decided it was sufficient to put an old sock in there instead :naughty:
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Re: 87 KDX 200 Bogging @ half throttle

Post by KDXGarage »

If it was ran with a sock, then the carb could be wore out or engine parts worn down. That is a huge no no.

If the engine and carb didn't get damaged, then a dirty carb is the first thing to look at.
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

I've already had the carb apart and cleaned it thoroughly. None of the parts were bad from what I could see, although I'm no expert. And the sock was in the stock air box held in place by the stock air filter cage, it wasn't just crudely attached to the end of the carb atleast
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87 KDX 200 Bogging @ half throttle

Post by targetman »

Did you see what size jets were installed?
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Re: 87 KDX 200 Bogging @ half throttle

Post by KDXGarage »

The oil catches the dust, not the filter... or sock.


Power valves or reeds? Get a new gasket before taking reed cage off
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

I don't remember what size it was, I'm going to tear into it further this weekend. What is the correct size I'm looking for though? And if they are the wrong ones where can I find the right ones to order?

Also is it better to keep the stock air box and just get a new filter for it, or delete the box and just get a filter that attatches right to the carb?

Sorry for the newb questions

Edit: The reeds are fine as well, no chips, although there is a slight gap between them, I believe there is supposed to be some but not sure if it's too much.
And as far as the power valve goes I'm at a complete loss with it, I know nothing about them or where it's even located, or how to check if it's functioning
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Re: 87 KDX 200 Bogging @ half throttle

Post by KDXGarage »

Can you post a VIN and engine number to make sure it is indeed a 1987 model?

You might want to look on eBay and buy an "Owner's Manual & Service Manual" for it.

If it is a 1987: https://www.ebay.com/itm/Genuine-Kawasa ... SwbE9a6bTU

Parts diagrams I always use: https://www.partzilla.com/catalog/kawas ... -kdx200-c2

You can get some of the carb parts from a store that sells genuine Mikuni parts. (Sudco, jetsrus)

Please get a new air filter instead of a clamp on filter.

My favorite brand: https://www.ebay.com/itm/Twin-Air-15135 ... SwDmBY5Aa9

next favorite brand: https://www.ebay.com/itm/1986-1988-Kawa ... 5954!US!-1

https://www.rockymountainatvmc.com/p/93 ... Filter-Oil

https://www.rockymountainatvmc.com/p/93 ... Filter-Oil

The reed valves should lay flat, with no gaps.

Power valves are in the cylinder. A centrifugal force on a ball and ramp mechanism activates a lever which pulls a rod. The rod has teeth on it. Gears with teeth are against the rod. When the RPMs reach about 6,000, the rod goes out, spinning the subvalves to alter exhaust flow. The little metal cover on the right side has some of the parts inside it.
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

So I just did a compression test today out of curiosity while I wait for parts. And my bike read about 135ish, my manual says standard is 156-186, and usable is 119-186. Am I okay to use the bike as is, or should I do a top end on it?
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Re: 87 KDX 200 Bogging @ half throttle

Post by KDXGarage »

That's warm or cold? I forget. Which way does the manual say to do it?
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

The manual says to do it warm, which makes sense. But I didn't realize that and did it cold, which is how I've always done my compression checks anyways, so its what I was used to.
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Re: 87 KDX 200 Bogging @ half throttle

Post by bufftester »

Aside from the stuff already mentioned, KIPS valve system and check flywheel/stator. 135psi cold isn't too bad, definitely still rideable. If the reeds are gapped at all they need to be replaced. At that age if they are the OEM they need to go.
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

The power valve is the next thing I'm going to check out when I have time. The reeds do have a gap, and they're definitely getting replaced. I was thinking about getting this to replace the whole thing, any thoughts?
https://m.ebay.com/itm/Moto-Tassinari-V ... %7Ciid%3A1
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Re: 87 KDX 200 Bogging @ half throttle

Post by KDXGarage »

If you don't mind me asking, what is your budget on the bike? Normal reeds and some other needed work might be better than VForce 3 right off the bat. Just asking.
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

I am on a bit of a budget, I don't have a dollar figure in mind, I just want to get it running properly. And I was considering the v force because they don't have screws to hold the reeds, the reason that interested me is because I noticed that my current reeds are missing one of the screws that holds them in place (no it didn't break off)
If there's a cheaper solution though I'm open to suggestions
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Re: 87 KDX 200 Bogging @ half throttle

Post by KDXGarage »

Image

$1.03 if you sign in to see the price on Partzilla.

https://www.partzilla.com/product/kawas ... 6100e57e02

Dirt bikes are money pits. There are many more things on the bike to suck money out of your wallet. :mrgreen:

If they are stock reeds, take them off, flip them over and blue Loctite the screws and reinstall. It may be flatter than it is now.

If you ever take the front wheel off and it has the stock tripmeter drive unit on the right side, BE CAREFUL to line up the tabs on the plastic piece inside the drive unit that matches up to the hub. I damaged mine back around 1989. Jeff Fredette repaired it back then.
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

Thank you! I'll have to check out partzilla when i get off work. And yes it has the tripmeter on the side, but the cable was hanging loose and it looks like he caught the front tire on it, so it may need repaired
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Re: 87 KDX 200 Bogging @ half throttle

Post by KDXGarage »

Image

reference number 11021A shows the part. It is on the inside of it.

Here is one on eBay (not mine).

Image
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87 KDX 200 Bogging @ half throttle

Post by RoostRider »

Update on the bike

Bought new boyesen reeds, screws from partzilla for the reeds since it was missing a few, got a new twin air filter and oil for it, recommended by Jason. A new carb boot and also bought new gaskets for what I took off and put them on. After I bought all the parts and installed them I was still having issues, so I took apart the cover for my power valve and noticed that the screw in the middle wasn't in the hole and was instead laying behind the arm that works my power valve, i put that back in and now it runs great, plenty of power, and it loves riding at high rpm now. Appreciate all the help guys, you rock! :supz:
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