98 KDX 200 lost compression

Discussion specific to the 1995 - 2006 KDX200 (H Series) and 1995 - 2005 KDX220R (A Series) models sold in the USA
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98 KDX 200 lost compression

Post by JakerB »

Two days ago I bought a 98 KDX 200 and I rode it yesterday day morning and it died on me, I assumed it ran out of gas because after hauling it home I flipped on the reserve and it started first kick. That evening I went to ride. The bike started and I rode for about 15-20 minutes before I was about half throttle in 6th gear cruising at somewhere around 5-6k rpm I’m guessing for a quarter mile of that and it died. I went to kick it and it had very little compression (I don’t know how no compression feels) you can feel the strokes but nowhere near enough compression tor it to run. Also tried removing the reeds, but I can’t get the reed cage loose. I did read that you shouldn’t pry on it and just tap it with a rubber mallets At the time I only had a pair of channel locks so I tapped it with that and couldn’t break it loose. So far I only took the carburetor and the reed/intake boot off. Haven’t had anymore time to tear into it.

So far I think it could be a gasket, the piston, rings, the reeds, or a seal. I’m not familiar with the KIPS enough to know if it can cause loss of compression. Or could it be something else that went wrong. This is in fact my first 2 stroke bike and am not familiar with 2 strokes as far as possible problems go.

Any advice, information, suggestions would be great.
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98 KDX 200 lost compression

Post by SS109 »

I know it's seems like a dumb question but did you have 2T oil mixed in with your gas? Assuming you did, The bike might have been running lean and toasted the top end. You need to do compression and leak down tests to narrow it down without disassembling the engine. Power valves do not affect compression.
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Re: 98 KDX 200 lost compression

Post by KDXGarage »

Welcome to kdxrider.net.

Read up on high speed throttle roll off and see if that sounds like your situation. Take the exhaust pipe off and have a look inside the cylinder. You may see some of the problem that way. Eventually, you will have to tear it all down.
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Re: 98 KDX 200 lost compression

Post by doakley »

Jason is correct
Of course. Might as well just take the top end off . Only way you will know for sure what’s in it.
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Re: 98 KDX 200 lost compression

Post by JakerB »

So I just did a compression test. 49 psi. Which is no where near enough. So I was able to get the reed cage out and I saw scoring on the piston. The spark plug was in fact a grey/white color so it was pretty lean and it got pretty hot. So I know I have to do a top end rebuild, still unsure of the cylinder wall condition. Probably needs to be re-machined. From there I’ll figure the bore if it’s the stock 66mm or not.

Yes there was a 32:1 mix of outboard 2 stroke oil. (Which I was kinda leary about)

So my question now is. Can I do an inframe top end rebuild? After that, How exactly should I break it in? I was given advice to run a regular 2 stroke oil to help seat the rings and piston by wearing them in and then use full synthetic to keep it that way. How long should I break it in? I did see someone say to get it up to temp and let it cool. Then ride it at a conservative speed and then rip it and give it the onions.
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Re: 98 KDX 200 lost compression

Post by KDXGarage »

You can disassemble the top end without pulling the motor.

What is the spark plug number that was in the bike?

One issue is whether your cylinder is plated (stock) or someone sleeved it in the past. Post a few cylinder pictures if you can. You can use a third party hosting service and link to them within the thread using the "IMG" tags.

If you spend the money on a replate, new piston kit, etc., you may want to buy some motorcycle oil for it.

You may want to buy a service manual. It will be the best money you can spend on the bike.

Don't get too upset as the repairs go along. Take a breather and read up on issues / ask questions.
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Re: 98 KDX 200 lost compression

Post by JakerB »

Ok. I will check the spark plug number tomorrow and check my gaps then as well. I plan on pulling the cylinder tomorrow and I can get pictures to see if it’s sleeved. I do have a manual, and I’m not going to rush this. It will be done right.

Sunday evening I’m going out of town so I need to get it pulled off and get my measurements to order a piston kit. If the cylinder needs replated or resleeved I’ll have to wait till Wednesday to get it worked on unless it just needs a sleeve ordered.

It’s best if I can get my parts Thursday I can put it all back together and can then break it in.
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Re: 98 KDX 200 lost compression

Post by KDXGarage »

Whether nickel-silicon carbide or iron / steel, the liner may be damaged. Unless you know something we don't, it may take a bit for it to be fully repaired.
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Re: 98 KDX 200 lost compression

Post by JakerB »

I’ve got a box of ngk BR9ES that came with the bike
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Re: 98 KDX 200 lost compression

Post by John_S »

Use BR8ES instead of 9. My guess the engine has a bad air leak and the sustained mid range rpm running got it hot. Read up on leak down testing for when you put it back together. It would've been good to do a leak down before tearing it apart but the main thing is it doesn't have an air leak when it's back together.
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Re: 98 KDX 200 lost compression

Post by KDXGarage »

Yes. Skip the 9s
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Re: 98 KDX 200 lost compression

Post by JakerB »

Ok, so there’s a small gouge in the wall and a little knick. (Probably from ring) The piston also has burnt in there as seen in the pics. I think I’ll get it bored over 30 thousandths or a bit more and then get it honed and cross hatched. My other option is to send it to Eric Gorr and get the 225 kit done to it either way it doesn’t matter unless there are horror stories of that 225 kit that I didn’t find. Image Image Image Image Image
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Re: 98 KDX 200 lost compression

Post by KDXGarage »

Stock is plated. Unless someone sleeved it in the past, one cannot bore it out. Also, DO NOT hone a plated cylinder.

I have read a few reviews of the 225 (223 actual) kit. It sounds great to me. :supz:
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98 KDX 200 lost compression

Post by SS109 »

Ditch those plugs like already mentioned. From the pics that top end is hammered. From what I can tell it's going to need to be replated. Please get some 2T oil made to be used in hurt bikes. BTW, you never said what your jetting was and at what elevation?

As for breaking in a new top end, regular or full synthetic 2T will make no difference. Just pick a good one and stick with it. My procedure is to warm up fully then shut it off to completely cool down and inspect for any leaks. If all is good, warm bike fully and your ready to ride. I normally start by riding it easy until I know the engine is fully warm (takes only a couple of minutes) then I'll hold it in 2nd gear and wind it up pretty good. Then I'll chop the throttle and let the engine slow the bike down low and then rev it out again. I repeat the rev/engine brake process about 10 times. This sets the rings really quickly. After that, let'r rip tator chip!
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Re: 98 KDX 200 lost compression

Post by JakerB »

Ok wait a minute. So if it’s not good to hone a plated cylinder, how do you get cross-hatching in there.
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Re: 98 KDX 200 lost compression

Post by KDXGarage »

I didn't catch that there were pictures. I have now looked at them.

It needs a replate. When the plating company plates it, they have special diamond hones that will put a cross hatch. You won't be cutting into the plating with a standard cheapie hone that is used on steel or iron cylinders. You might flake off the thin and brittle plating though.

In the manual, it states, DO NOT bore or hone an Electrofusion cylinder.

Read up on plating. I STRONGLY suggest that you do not have it sleeved. That is a downgrade.

A plater dips the cylinder in a chemical bath to strip off the old plating, then ensures roundness and replates and hones the new plating.

Read up on plating at the PowerSeal USA or Millennium Technologies websites.
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Re: 98 KDX 200 lost compression

Post by KDXGarage »

This should help.

Image

Image

Image

Image

Image
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98 KDX 200 lost compression

Post by JakerB »

Well it’s been two months. Bike is back together and running on my 3rd break-in cycle (I planned 4 with the second 2 riding it) so I checked my spark plug and it’s lean.

My pilot jet is 40 and my main is 152 the needle is 3rd from top and the air screw is 7/8 out. That’s how it came from RB designs and that’s what’s on the paper. I didn’t want to turn the air screw in much more but I did and rode for a couple minutes and it’s still lean.

I have a 42 pilot and a 155 main I’ll try tomorrow and I think I’ll richen the needle. I’m about 500ft above sea level. Then I should be able to have the needle 1.5-2 turns out.Image

Any help is appreciated, Thanks.
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98 KDX 200 lost compression

Post by SS109 »

Glad to hear it's back together. BTW, don't break it in easy. It's not good for ring sealing. One break-in ride is all it takes.
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Re: 98 KDX 200 lost compression

Post by JakerB »

At the end there I have a pic of the first plug. After 42 and 155 with 1.5 out I kept the needle 3rd clip down. I got this.
Image
And here’s the other side
Image

It also bogs right off idle but it clears when it’s warm so I thought I would back out my air screw a tad to clear that up.
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