1989 KDX 200 Basket Case Project

Got questions? We got answers....
Post Reply
Koko
Member
Posts: 100
Joined: 07:05 am Jun 15 2012
Country:

Re: 1989 KDX 200 Basket Case Project

Post by Koko »

I wish i could help you mechanically. But I can't. All I have to say is don't give up. The bike looks great. Save up and rebuild the motor when money allows. you've come way to far.

Sent from my mobile device with horrible battery life.
gwynfryn
Member
Posts: 41
Joined: 05:51 pm Feb 04 2012
Country:
Location: New Zealand

1989 KDX 200 Basket Case Project

Post by gwynfryn »

Sounds just like my bike. Scored piston isn't flash though. It might not seem so bad after a good sleep.
KDXrider1989
Member
Posts: 643
Joined: 09:05 pm Sep 07 2010
Country:
Location: Houston, TX

Re: 1989 KDX 200 Basket Case Project

Post by KDXrider1989 »

sounds just like my bike also, and I have a good cylinder last time I checked. Just throwing some ideas out there, but did you fill the radiators with the correct amount of antifreeze, the right type, and bled the system of air? or maybe carburetion/jetting issues?
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

Re: 1989 KDX 200 Basket Case Project

Post by Thrahl »

KDXrider1989 wrote:sounds just like my bike also, and I have a good cylinder last time I checked. Just throwing some ideas out there, but did you fill the radiators with the correct amount of antifreeze, the right type, and bled the system of air? or maybe carburetion/jetting issues?
They were filled with 50/50 mix. I filled them, ran it a bit then topped them off. The water flows strong, I can see it pouring in to the top of the rad.
The rads were getting hot too so I know that they were transferring heat.

The cylinder gets hot, like you can't touch it for any length of time without pulling your hand away. You can hold your hand about 1-2 inches away all day though. I just don't know how hot is too hot.

I'm beginning to think maybe it is something to do with timing. That would affect the 1/2 throttle full rpm problem I believe and could make the engine run too hot or knock like it is. I'm not really sure.
I'm going to pull the flywheel and see if my woodruff key maybe sheared, though I was extremely careful to make sure it wouldn't. I lined the timing marks up properly and tightened everything down so I highly doubt they moved.

When I was talking with my dad about it he was saying the only thing I didn't check when I rebuilt everything is if the rod is bent. I checked for big end bearing movement and made sure the rod didn't rub the crank or anything but I didn't actually check for straightness in the rod. Idk if that could have been the issue, I will have to take it apart to tell that.
chkdx
Supporting Member I
Supporting Member I
Posts: 132
Joined: 09:31 pm Oct 02 2009
Country:
Location: Carson City, NV

Re: 1989 KDX 200 Basket Case Project

Post by chkdx »

It's normal for the engine to rev up quickly and very high in neutral with very little throttle. 2 strokes typically rev much quicker than 4 strokes.

Just curious, what oil / gas mix ratio are you using? I hate to ask, but maybe you forgot to put oil in the gas?
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

Re: 1989 KDX 200 Basket Case Project

Post by Thrahl »

chkdx wrote:It's normal for the engine to rev up quickly and very high in neutral with very little throttle. 2 strokes typically rev much quicker than 4 strokes.

Just curious, what oil / gas mix ratio are you using? I hate to ask, but maybe you forgot to put oil in the gas?
It's not just in neutral. If I drive it down the street, it is reaching close to max rpm around 1/2 throttle.
Aside from the damage obviously, the throttle issue makes it not ridable because I am getting full power with just the slightest twitch of the throttle.
The wheel is spinning or the front end is lifting by just rolling on to 1/4 throttle.

I am running 32:1 Bel-Ray 2 stroke oil with 93 octane gas. I was very careful to make sure I mixed it all properly.
User avatar
scheckaet
KDXRider.net
KDXRider.net
Posts: 3740
Joined: 12:09 am Nov 10 2005
Country:
Location: edmond oklahoma

1989 KDX 200 Basket Case Project

Post by scheckaet »

air leak somewhere? causing a lean condition?
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

1989 KDX 200 Basket Case Project

Post by Thrahl »

scheckaet wrote:air leak somewhere? causing a lean condition?
I guess it's possible. If you look at the last page though I checked, double checked, and triple checked for air leaks with my little leak tester and fixed everything I found, which wasn't much.
I'll probably plug it back up and check again but it didn't seem like it was running lean or anything. air screw seemed best close to 1.5 turns out, rpms returned to idle normally I'd say (you can watch my video and see what you think), i didn't notice any hesitation, backfiring, sputtering, or anything while riding at any throttle range.

Honestly, if I hadn't taken off the pipe and seen the piston and cylinder I wouldn't have known anything was wrong aside from the throttle issue.
chkdx
Supporting Member I
Supporting Member I
Posts: 132
Joined: 09:31 pm Oct 02 2009
Country:
Location: Carson City, NV

Re: 1989 KDX 200 Basket Case Project

Post by chkdx »

Another possible air leak source that wouldn't have shown up with the leak tester, is where the exhaust pipe joins the cylinder. If that joint is not air tight, it can cause you to run lean. Are the o-rings on the pipe in good shape? It's also a good idea to use a little hi-temp silicone on those o-rings to make sure that joint is really sealed up well.
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

Re: 1989 KDX 200 Basket Case Project

Post by Thrahl »

chkdx wrote:Another possible air leak source that wouldn't have shown up with the leak tester, is where the exhaust pipe joins the cylinder. If that joint is not air tight, it can cause you to run lean. Are the o-rings on the pipe in good shape? It's also a good idea to use a little hi-temp silicone on those o-rings to make sure that joint is really sealed up well.
The o-rings were freshly replaced. There was no smoke or spooge coming from there so I would assume no serious amount of air was entering.

I will probably work on it this weekend. I'm not in any rush though because regardless of what caused the problem I'm not going to keep dumping money into it right now.
I'm looking at at least another $300 for another replate and piston and that is assuming something in the bottom end wasn't the cause of the failure. We'll see.
User avatar
turtle
Supporting Member II
Supporting Member II
Posts: 460
Joined: 02:00 pm Jun 21 2010
Country:
Location: Central IL

1989 KDX 200 Basket Case Project

Post by turtle »

The bike looks awesome! Hang in there and make it right when your circumstances allow it. I'm sure you'll be glad you did in the end.
Bill
Central IL
2004 KDX220R
2011 Triumph Tiger 1050 SE
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

1989 KDX 200 Basket Case Project

Post by Thrahl »

I messed with the bike a little more today. I was sort of hoping that the woodruff key on the flywheel had sheared because that would have made it jump time and is easy to diagnose and replace.
But it was fine and the stator was lined up perfectly between the marks.

Then I threw the leak tester on there and checked for a leaking crank seal and it was fine too. Pumped maybe 20-25 psi and no bubbles with the soapy water.
Checked everywhere else too, aside from the clutch-side crank seal, and everything checked out good.

So I put that all back together and thought maybe it was running lean around 1/2 throttle or something so I richened up the needle and put everything back together.
Started the bike on the stand and after letting it warm up it was still opening the KIPS around 1/2 throttle or so, though maybe it was very slightly better, it's hard to tell on the stand.
I don't really want to ride it with that nasty knock because I am pretty sure it is piston slap from the seizure locking a ring or something. Don't want to do more damage than there already is.

Anyone who watched my little video, aside from the obvious knock, did the bike not sound right to you?
I have been watching KDX and other 2 stroke videos and they all sound much more tinny and brappy than mine. Mine sounds dull and 4 strokish.
Dekon
Supporting Member II
Supporting Member II
Posts: 674
Joined: 07:54 am Jun 26 2012
Country:
Location: Rhode Island

1989 KDX 200 Basket Case Project

Post by Dekon »

Just a thought here, but maybe someone put a quick throttle tube on it. The one on my Beta Rev 3 is like that. It is full throttle in 1/2 turn.
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

1989 KDX 200 Basket Case Project

Post by Thrahl »

Dekon wrote:Just a thought here, but maybe someone put a quick throttle tube on it. The one on my Beta Rev 3 is like that. It is full throttle in 1/2 turn.
I put the throttle tube on it. It was a $20 set from eBay so it could be anything.

Maybe I am getting something mixed up here but full throttle should be when the slide is all the way up in the carb right?
As in it should just keep revving and revving until the slide is 100% maxed at the top.
That's how it is on everything that I have ever worked on but maybe 2 strokes are different.

Basically I am hitting max rpm when the carb slide is only about 1/2 way up the carb, therefore not letting the maximum amount of air through.
User avatar
Julien D
KDXRider.net
KDXRider.net
Posts: 5858
Joined: 07:53 pm Nov 07 2008
Country: USA
Contact:

Re: 1989 KDX 200 Basket Case Project

Post by Julien D »

So you don't know what bike the throttle tube came from? They are cam driven, and different bikes have different setups. Could be related. It's difficult to monitor the action of the slide vs throttle position when the carb is assembled and on the bike.

The bike will continue to rev out at half throttle depending on the amount of load. On a flat section or slight downhill, it could be possible to reach nearly max RPM at half throttle.
Image
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

Re: 1989 KDX 200 Basket Case Project

Post by Thrahl »

Julien D wrote:So you don't know what bike the throttle tube came from? They are cam driven, and different bikes have different setups. Could be related. It's difficult to monitor the action of the slide vs throttle position when the carb is assembled and on the bike.

The bike will continue to rev out at half throttle depending on the amount of load. On a flat section or slight downhill, it could be possible to reach nearly max RPM at half throttle.
Since the slide is directly linked to the throttle I would imagine that once the grip is twisted all the way and stops then the slide is all the way open.

I guess 2 strokes are different from 4 strokes in that rpm basically corresponds with throttle position. As in, half throttle, about half of max rpm, full throttle, max rpm, etc.
All of my testing was either done on the stand or on flat concrete, so not much resistance.
Idk none of this really makes much sense to me but if that is the way it is then that is the way it is I guess.

I might be able to tear apart the engine tomorrow, but I will be working on my car so maybe not.
Looking through the exhaust I can see a seize on the left and right of the intake, but not the middle. I have a feeling it's going to be a four corner seizure. We'll see.
dfeckel
Platinum Member
Platinum Member
Posts: 644
Joined: 07:46 am Nov 09 2009
Country:

1989 KDX 200 Basket Case Project

Post by dfeckel »

Does your compression feel altered at all? A seizure that damages the rings would probably result in lower compression. Do you have a compression tester? If so, test it and compare the number with your initial number (hopefully you took a before measurement).

Half throttle is a LOT of throttle, at least the way I ride. A steady half throttle WILL give you max RPM at light loads, even on a 4 stroke. KIPS opening when revving the throttle to half way on the stand is perfectly normal in my opinion.

Is the bike still starting well?

Try to get a good picture with the pipe off and post it up on here. Maybe pull the reeds off, too and get a picture from the intake side. Let us see what streaking you see. So much of what you describe as abnormal running behavior sounds normal to me that I'm concerned what you're seeing on the pistion might qualify as normal scuffing. Show us the pics before you tear anything down.

I know what it's like to have to re-rebuild a motor, and it sucks a bunch. I'm hoping that you have psyched yourself out and there's nothing wrong with your top end. Worst case, you have to redo it and it'll go three times faster because you know how to do it already.
David Eckel
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

1989 KDX 200 Basket Case Project

Post by Thrahl »

dfeckel wrote:Does your compression feel altered at all? A seizure that damages the rings would probably result in lower compression. Do you have a compression tester? If so, test it and compare the number with your initial number (hopefully you took a before measurement).

Half throttle is a LOT of throttle, at least the way I ride. A steady half throttle WILL give you max RPM at light loads, even on a 4 stroke. KIPS opening when revving the throttle to half way on the stand is perfectly normal in my opinion.

Is the bike still starting well?

Try to get a good picture with the pipe off and post it up on here. Maybe pull the reeds off, too and get a picture from the intake side. Let us see what streaking you see. So much of what you describe as abnormal running behavior sounds normal to me that I'm concerned what you're seeing on the pistion might qualify as normal scuffing. Show us the pics before you tear anything down.

I know what it's like to have to re-rebuild a motor, and it sucks a bunch. I'm hoping that you have psyched yourself out and there's nothing wrong with your top end. Worst case, you have to redo it and it'll go three times faster because you know how to do it already.
No unfortunately the top end is definitely messed up, not psyching myself out there.
I didn't even have time to take an initial compression reading. By the time I finished my final break in session I realized it had messed up.
But the compression is much lower than it should be. I'm sure a ring is stuck. Not going to even bother compression testing.
It also takes many many kicks to start when cold, probably about 30 or so.

I'll get pics of the cylinder when it is off the bike.

I have been doing research and a lot of people say that if it is a minor seizure, many times you can get away with just cleaning everything up and slapping it back together.
Specifically, the cylinder is usually not damaged, it just gets the piston's aluminum smeared on the walls and it can be removed with a little muriatic acid and a scrotch brite.
The piston will most likely have to be replaced though. But $93 is a lot better than $300 if I can get the cylinder cleaned up good.
dgraver1
Member
Posts: 9
Joined: 03:06 am Aug 04 2012
Country:

1989 KDX 200 Basket Case Project

Post by dgraver1 »

good luck and good work so far. I know exactly the sick feeling your talking about when you see all your time effort and money just take a dump infront of you. I did what you were talking about the with wristping circlip. I did seat it correctly and chewed my newly plated cylinder from langcort, and newly RB worked head and new wiseco. made me sick.

dont give up. I just started back working on mine and i am taking my time this time around.
dfeckel
Platinum Member
Platinum Member
Posts: 644
Joined: 07:46 am Nov 09 2009
Country:

1989 KDX 200 Basket Case Project

Post by dfeckel »

My first case splitting was the result of a top end seizure in the first five hours of running my newly assembled hybrid. My donor KDX motor had a good bottom end, so I just did the top, including powerseal, RB, Wiseco. First big ride was a hot, dusty day and it seized. I was miserable. It turns out I didn't have the air boot tightened on the KDX carb. Not that big a deal on anything except my hybrid, since the KX boot is a good millimeter too big for the KDX carb. It sucked dirt and boom.

I had to replate the cylinder and get a new piston, so while that was being done, I decided to split the cases and do my bearings and seals. All went well in reassembly until I realized I couldn't find the pin that goes between the shift drum and the star thingy. I couldn't find it anywhere. I was pretty sure it wasn't in the transmission, but I had no way to know except to split the cases AGAIN. :? I just love scraping off case sealer!

The bright side? Doing the job twice in quick succession ingrained the knowledge on how to do it permanently on my brain. Manuals? We don't need no stinking manuals!

Good luck. You'll get it figured out.
David Eckel
Post Reply