KDX200 - what happened to my top end???

Green Streak

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Aug 10, 2001
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Hi All,

This is my first post in this forum and I am hoping someone out there has an idea of what is wrong with my bike.

I have an 87 KDX200 that has no power in the top 1/2 of 1st and 2nd gear. I have to short-shift these gears in order to ride it w/o it over reving.

I had the clutch plates changed thinking this would cure the problem but it did not. Could it be a carb / jetting problem??

Any (logical) suggestions would be greatly appreciated!

GS
 

spanky250

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Dec 10, 2000
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Does the bike work ok in the other gears, and only seem to blow through first and second? If so, my thought would be that someone has put a too small front sprocket on it, making first and second so low that they have become useless.
 

Green Streak

Member
Aug 10, 2001
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other gears work fine. The spocket has not been changed (for a long time). If the teeth are worn on the front sprocket could that cause the problem only in the 1st 2 gears?
 

spanky250

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Dec 10, 2000
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Does the bike seem to run correctly, in any gear? Does it blubber, or miss in the lower gears, or just seem to go flat? If you hold it in third, does it continue to pull strongly as it revs? Has this been a problem that developed gradually, or all of a sudden? And no, a worn sprocket would affect all the gears.
 

dirt bike dave

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May 3, 2000
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Yes. Your engine has more mechanical advantage over the chain/sprockets in the lower gears, so it would be more likely to spin the sprockets inside the chain in the low gears. But this would only happen if one or more sprockets and/or chain are totally worn out. Are they? :D

BTW, each tooth on the front sprocket gets used about 4 times as often as the rear, so it is not uncommon for the front to wear out first.
 

spanky250

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Dec 10, 2000
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Dave, I would think that a sprocket that is so worn that the chain slips around it would likely have no teeth left on it after even one ride (I'm guessing, I've never worn one out that badly:confused: ), so it would be noticeably slipping under any load wouldn't it? And it would certainly be very noisy when the chain slipped over the nubs, so that should be easily noticed.
 

Green Streak

Member
Aug 10, 2001
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I think I should replace the front sprocket as it does have some teeth in a pretty worn state.

As for Spanky's questions - the problem seemed to come about quickly and the 1 and 2 gears do go 'flat' almost immediately after cracking the throttle (If I kept it in first I would still keep going but I would be reving way to high). In 3rd it is fine, I can get on the pipe and it pulls fine.
 

dirt bike dave

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May 3, 2000
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Spanky,
I've never worn one anywhere near that bad, either. But I saw a guy with an XR once and it was pretty amazing that he could still ride the bike. If a normal front sprocket tooth looks like the Himalaya mountains, his were like the Appalachians. I can see how it would hook up under low load but spin inside the chain at WOT in low gears. It might not make a lot of noise, either, if the teeth are 'filed down' that far, but would feel more like the clutch slipping (which is also something Green Streak should look into).

I've also heard of one or more teeth breaking off, but I think that would be easier to notice than even but extreme wear.

IMO, the front sprocket should be replaced more often than the rear and the chain. The $15 worn out front sprocket will accelerate wear on the $50 rear sprocket and $80 chain. My theory is to replace the cheapest, fastest wearing part before it trashes the other bits.
 

Green Streak

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Aug 10, 2001
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here is a pic of my sprocket - obviously smaller than factory. I will replace and see what happens....

Spocket.jpg
 

dirt bike dave

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May 3, 2000
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Yeah, that one should have been replaced long ago. When you get a new one, lay the old sprocket on top to compare how much it has worn. Long before the front sprocket wears as much as yours it is causing premature wear to your chain, IMO.

If your chain and rear sprocket are also worn out, they will quickly wear out your new front sprocket, so you might consider a whole set.

With some bikes, you can extend front sprocket life by flipping it over. But the time to flip it is before it gets worn out.
 
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Green Streak

Member
Aug 10, 2001
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thanks for the help. I will replace sprocket and check out the chain as well. Once done I'll let you know how it runs. Hopefully this is the fix.

Blue Strreak
 

spanky250

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Dec 10, 2000
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That sprocket is worn, as evidenced by the "hook" shaped teeth, and it definitely needs replacing, but the length of the teeth is still fine, so your problem isn't a slipping chain, unless it is the rear sprocket that is worn enough to allow the chain to slip over the teeth. I would also rule out a slipping clutch, as they slip worse in higher gears, the opposite of your problem. Is the power-valve opening properly? If it is stuck closed, the engine would make very poor power at higher revs, making it seem like the powerband stops short. It is not as noticeable in the higher gears, because it takes the engine longer to reach the revs where the power falls off.
 

JohninKY

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Nov 18, 2000
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Originally posted by Green Streak
(If I kept it in first I would still keep going but I would be reving way to high). In 3rd it is fine, I can get on the pipe and it pulls fine.
If the motor revs higher and the bike isn't accelerating doesn't that mean something is slipping? I'd lay money it's the clutch.
Doesn't sound like a power valve problem. The sprocket doesn't look worn enough to slip. Being a cheap ******* I occasionally run sprockets until the teeth break off so I may be an expert on the subject. If your running a chrome moly front and aluminum rear the front will last about twice as long as the rear even though each tooth sees four times as much use.
 

spanky250

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Dec 10, 2000
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Well, the clutch is very easy to test. Pull the front wheel up to a tree, or some other solid object, shift into top gear, grab a handful of throttle, and let out on the clutch. If it is slipping, the engine will stay running, if it is not slipping, you will kill the engine.
 

Green Streak

Member
Aug 10, 2001
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Thanks for the tip onn how to check my clutch. I hope it is not my clutch though as Johnin KY thinks. As I mentioned in my original post - I thought it was my clutch as well, and had my clutch plates replaced (friction plates were OK).
 

spanky250

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Dec 10, 2000
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Just make sure you do it in top gear. If you try it in a lower gear, and the clutch is ok, you might just find yourself climbing that tree.:eek:
 

GreenMan

Member
Feb 1, 2001
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I have worn a sprocket out to the point of it slipping and that sprocket will not slip. I would check the back sprocket as well. Remember the back sprockets are aluminum most of the time. Many of the aftermarket rear sprockets are aluminum. The tree test is a good one. Make sure to have a friend observing to see if the chain is slipping.

If he has a camcorder maybe you can win $10,000 on funniest videos just in case you want to try it is first gear.

I suppose mentioning the rear tire condition is a bit obvious. I have learned to not overlook the obvious. If it is nothing in the threads above then you are talking clutch or gears.

Let us know what you find.
 

dirt bike dave

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May 3, 2000
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His front sprocket pic does show some teeth remaining and looks like it shouldn't slip, but we don't know if the chain is badly kinked or improperly adjusted.

If the clutch hadn't been replaced, I would say that could well be the problem. It wouldn't hurt to double check the adjustment.

FWIW, the '86-'88 usually have a strong hit when they come on the pipe, so I'm guessing that is when the slipping occurs.
 

goldman15

Member
Jun 9, 2001
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Have you figured out what the problem was?

Greenstreak I have the exact same problem with my 95 KDX 200. Good throttle response in 1 and 2nd gear but falls flat at half throttle. 3rd gear on up is fine. Please let me if you have found out how to fix this problem. Thanks
 

dirt bike dave

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May 3, 2000
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Goldman, you're problem is probably jetting - most likely too rich on the main jet or needle too high (clip in too low a groove). There is less load on the engine in the lower gears, so the fuel requirement is less and you sound like you're getting too much fuel. If the weather is hot & humid and your air filter is dirty, this could make the overly rich jetting worse. Make sure you have a fresh plug, too.

With Green Streak's bike, it sounds like in the low gears the bike will rev really high but not accelerate, indicating something is slipping somewhere.
 

RM250Rida

Member
May 16, 2001
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Make sure the clutch cables adjusted properly. It may be adjusted too tight causing the clutch to be slightly engaged when the lever's not being pulled at all. I like to adjust mine so that you can move it back and fourth just a tad bit with out the arm moving at all. Its a sure fire way of knowing it's not to tight.
 

Green Streak

Member
Aug 10, 2001
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Re: Have you figured out what the problem was?

Originally posted by goldman15
Greenstreak I have the exact same problem with my 95 KDX 200. Good throttle response in 1 and 2nd gear but falls flat at half throttle. 3rd gear on up is fine. Please let me if you have found out how to fix this problem. Thanks

I plan on getting the new sprocket today and also am going to check out the chain and replace if required (rear sprocket looks ok). I'll keep you tuned. I think I'll also check out my jetting as well.
 

roostinbe

Member
Mar 22, 2001
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i must say, i am surprised no one has mentioned the engagement cogs, on the enternal gears. on a bike that old, (especially a trail bike) it wouldn't be uncommon for the internal 1st, and 2nd gears to be worn out. if it was ridden on tight trails, or by someone really slow, then it would be in 1st, and 2nd most of the time, which could cause what you are talking about. it is for sure not going to be the final drive system, because that would effect all of the transmission. and its not going to be the jetting, because he said it would rev out. thats just the way i see it.:eek:
 

Green Streak

Member
Aug 10, 2001
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Originally posted by roostinbe
[B if it was ridden on tight trails, or by someone really slow, then it would be in 1st, and 2nd most of the time, which could cause what you are talking about. [/B]

;) well....I'm not THAT slow.... however I do use first and second gear a lot since I do ride fairly tight trails.

I removed my carb and am going to replace my main and pilot jets with the stock components. I didn't get my sprocket today because the &$##@! store was closed. I also removed my chain and measured it. It's within it's usable limit.

All of the advice is great. If the sprocket or jetting does not fix it I'll check out the gears. By the time I'm finished I may have replaced everything!

I love this bike - the only thing I hate about it is that it doesn't have a rear disc brake.
 

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