1989 KDX 200 Basket Case Project

Got questions? We got answers....
Post Reply
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 »

Any updates on this?
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

1989 KDX 200 Basket Case Project

Post by Thrahl »

Well I have been putting it off for a while because I have been busy and honestly was just tired of messing with it.
But today I have the day off and decided I would tear the engine apart and see what's up.

A turn of events though, the piston and cylinder look fine. There are very light scratches that I can't even feel with my fingernail and that's about it.
I was expecting a big seize that locked the rings, causing the knocking, low compression, and hard starting. But the rings are perfectly fine.
Here are some pics that I took. I enhanced the contrast/brightness/color so that you could more clearly see the marks. They don't look as bad in person.
Image
Image
Image
Is that too much blow-by on the exhaust side for a perfectly fresh engine? The top of the piston is just a very light brown.

Something that caught my attention though is the amount of side to side play the piston has. It doesn't move up or down, nor does it twist or anything, but it can slide left and right a lot.
The majority of the play seems to be the piston sliding on the wrist pin and bearing. Here is what it looks like from the intake hole.
Image
I will post a video shortly.
EDIT: Here is the video link
To me it seems excessive, and I could see how it could possibly cause the knocking I was getting. Any ideas?

Overall though I am kind of kicking myself for not taking it apart sooner because I could have fixed it and been riding. Oh well, atleast I am not out $300. :supz:
david
Member
Posts: 524
Joined: 08:30 pm Oct 10 2011
Country:
Location: Forney, TX

1989 KDX 200 Basket Case Project

Post by david »

Side to side movement of the piston is not a concern.
'81 KDX 175
'90 KDX 200
'07 Vulcan 2000 Classic LT (totaled 4/25/15)
'82 Honda GL500 (sold)
'96 ZXi 1100 JetSki
'98 STX 1100 JetSki
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

1989 KDX 200 Basket Case Project

Post by Thrahl »

david wrote:Side to side movement of the piston is not a concern.
Did you watch the video? It just seems like a huge amount of play.
KarlP
Supporting Member III
Supporting Member III
Posts: 1484
Joined: 02:26 pm Jun 29 2005
Country:
Location: Alabama

Re: 1989 KDX 200 Basket Case Project

Post by KarlP »

You seem to be chasing two problems here - a knocking sound and an apparent loss of compression/possible seizure

It does not look like you had a seizure. That blow by looks fine for an unbroken in motor. I would put it back together and run it gently.

The knocking could be coming from a lot of places. KIPS gear, loose clutch hub nut, loose exhaust mounts, poorly fitting exhaust into cylinder....

KDX motors are kind of noisy. Several times I've done a piston and ring replacement, started it up, and had that sinking feeling.

You seem to overly concerned with throttle position and RPM. When on the stand that KIPS valve will operate at well under 1//2 throttle. I bet if you held it at 1/4 throttle it would open. Try blipping it to 3/4 throttle, it should just start to move and reclose as the RPM's drop.

Go riding, stay off the pipe for a bit, I think everything is going to be all right.

Take this advise for what it is worth. I am an engineer; it's surprising any of my stuff runs at all.
'08 KTM200xc
'99 CR/KDX Hybrid with that RB stuff done to it
KX100 for the boy
User avatar
Julien D
KDXRider.net
KDXRider.net
Posts: 5858
Joined: 07:53 pm Nov 07 2008
Country: USA
Contact:

1989 KDX 200 Basket Case Project

Post by Julien D »

I second all of Karl's points. Nothing I have seen here or heard you describe seems like a problem to me.
Image
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

Re: 1989 KDX 200 Basket Case Project

Post by Thrahl »

KarlP wrote:You seem to be chasing two problems here - a knocking sound and an apparent loss of compression/possible seizure

It does not look like you had a seizure. That blow by looks fine for an unbroken in motor. I would put it back together and run it gently.

The knocking could be coming from a lot of places. KIPS gear, loose clutch hub nut, loose exhaust mounts, poorly fitting exhaust into cylinder....

KDX motors are kind of noisy. Several times I've done a piston and ring replacement, started it up, and had that sinking feeling.

You seem to overly concerned with throttle position and RPM. When on the stand that KIPS valve will operate at well under 1//2 throttle. I bet if you held it at 1/4 throttle it would open. Try blipping it to 3/4 throttle, it should just start to move and reclose as the RPM's drop.

Go riding, stay off the pipe for a bit, I think everything is going to be all right.

Take this advise for what it is worth. I am an engineer; it's surprising any of my stuff runs at all.
The exhaust could be the ticket. The pipe has seen better days and the mount into the cylinder is tight but a little crooked. It also currently has no rubber damper brackets because I need to make them still.

When researching 2 stroke knocking people were saying pull in the clutch and see if it goes away. That would indicate something with the clutch. I hadn't tried that.
I will put it all back together, start it up, and if it is still knocking try to find the source.

I'll keep you all updated.
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 »

Sounds good. And remember, even the healthiest KDX sounds like a diesel on crack. They do knock.
Image
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

1989 KDX 200 Basket Case Project

Post by Thrahl »

Alright so I slapped it all back together. Compression felt much higher than it was. Tested at 175, which seems pretty good to me. Idk if it is really even fully broken in yet either.
Started up pretty easily but sounds about the same. Pulling in the clutch seems to change the pitch. I added a little bit more ATF in and that might have helped a bit more.
But it doesn't sound like an issue as much as I thought, it just sounds like a noisy engine.

I played with the needle position some until it pulled cleanly. I may adjust it a bit more later on.
It pulls hard off idle and all the way through the revs so I think the jetting is pretty close right now. I will do all of the proper testing soon to get it spot on.

Overall I am pretty excited again about this project though. I had lost interest because I really didn't want to put more money into an old bike that I had only ever see run for about 15 minutes.
But it seems to be fine. Still work to do though.

I have an oil leak somewhere. I can't see where it's coming from, just that it is very slowly dripping from the coolant drain screw only when the bike is running.
I also need to replace my water pump seal. There is a little bit of oil in my coolant and my oil sight glass is fogging up which I assume can only happen if there is water in there evaporating.
I need to make rubber mounts for my exhaust and make a rubber collar for the expansion pipe to silencer joint.
My fork seals are weeping as well and will probably blow out soon so they need to go.
There are a few other small things too but the engine is good now so that is the most important thing.

I will continue working on it though and update with pictures. I will also make a full video soon going over the whole bike and running it around with the GoPro on.
Koko
Member
Posts: 100
Joined: 07:05 am Jun 15 2012
Country:

Re: 1989 KDX 200 Basket Case Project

Post by Koko »

Way to keep at it. Glad to hear there wasn't a seisure!
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 »

you're fork seals may not be that bad, maybe just some trash stuck in there. Before you replace 'em, get something thin enough to fit in between the seal and the fork tube and go around 2 or 3 times, and see if you pick up any trash. I used old camera film and cut a hook into it, or you can just order a Seal Mate
User avatar
B737driver
Gold Member
Gold Member
Posts: 491
Joined: 01:11 pm Dec 02 2011
Country:
Location: Heath, Texas

1989 KDX 200 Basket Case Project

Post by B737driver »

A 2 smoke is made to be shifted into a higher gear. If it's revving too much at half throttle.....shift up if your trying to stay on the bottom end. Regardless of how much "grunt" the KDX has, it's not a 4 stroke, and that's a good thing in my mind. It is difficult to maintain a constant RPM on a 2 stroke at a certain throttle position. These things are made to go! Clutch work, and shifting is the key.

A 4 stroke may be able to to complete a trail or track in only a couple of gears, while on a 2 stroke you will you go through many more gears.

BTW, your bike sounds identical to mine. They call it the KDX rattle for a reason.

Not trying to sound prude. You've spent a lot of time and money building a great bike. I personally, don't see any issues with it.

Go ride, and enjoy a lightweight machine that is much more agile than a 4 stroke.

Just my opinion.
Live to Fly
Fly to Live
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

Re: 1989 KDX 200 Basket Case Project

Post by Thrahl »

Alright well I haven't updated in a while, been really busy with work and classes just started back up this week too.
I've done lots of little things on the bike but I will give an update to that later when I take pictures.

The other day I tested the main jet by cracking it hard from putting around to 100% throttle and it would bog hard for a second then take off. From what I read everywhere that is a lean condition.
So I went ahead and ordered a 155 and 158 main (there is a 152 in there now). The 155 came in first so I installed that today.
It is still bogging with the 155. If I pull the richener it acts as it should when I pop it like that.
I will need to play with it more and probably throw the 158 in. Hopefully I won't need to buy a size bigger, I WANNA RIDE! :supz:

I'm a little confused about setting the float height though. I am turning the carb updside down and measuring from the mating surface to the "crest" of the float (since it is triangular on the top).
But since the two measuring points are offset from each other it is difficult to get an accurate reading. Do you all have any tricks or suggestions to get a good reading?
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 »

I was stuck on this same problem about 2 weeks ago. What I did was get a piece of construction paper or something sturdy and thin, and measure whatever the manual says on float height and mark it onto the piece that you cut out. Stick it behind the float while making sure it's level with the mating surface, and adjust your float accordingly. Remember to measure when the pin spring IS NOT compressed, it's easier to do this when the carb is on its side
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

Re: 1989 KDX 200 Basket Case Project

Post by Thrahl »

KDXrider1989 wrote:I was stuck on this same problem about 2 weeks ago. What I did was get a piece of construction paper or something sturdy and thin, and measure whatever the manual says on float height and mark it onto the piece that you cut out. Stick it behind the float while making sure it's level with the mating surface, and adjust your float accordingly. Remember to measure when the pin spring IS NOT compressed, it's easier to do this when the carb is on its side
You know I heard something about the pin spring somewhere else but the manual didn't mention it anywhere.
So the float needle needs to be fully seated but the little pin in the middle of it needs to be fully extended? That would add atleast another 1mm or so to the measured height too.
I'll give it a shot next time I get a chance to work on the bike.
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 »

Keep in mind you are talking about a simple carbureted ICS engine. Cracking the throttle WFO from very low RPM is almost certainly going to cause some hesitation. I have a hard time thinking you need the 155, much less a 158.
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:Keep in mind you are talking about a simple carbureted ICS engine. Cracking the throttle WFO from very low RPM is almost certainly going to cause some hesitation. I have a hard time thinking you need the 155, much less a 158.
I mean if cracking hard with choke on reacts better than with it off then I should go richer right? I'm not riding long enough at low throttle to load up or anything. It would be like coming out of a corner to a straight away and cracking it hard.
But I thought the same thing about the jets since most people tend to go max 155, usually leaner.

This is just preliminary testing to get in the ballpark before I go do a plug chop. I don't want to be banging gears at full throttle if my main is way too lean and risk a seizure.

Maybe I am getting ahead of myself. I will start back over and adjust from pilot on up and see if it reacts any differently. Maybe my air screw isn't in the right position or something.
KarlP
Supporting Member III
Supporting Member III
Posts: 1484
Joined: 02:26 pm Jun 29 2005
Country:
Location: Alabama

Re: 1989 KDX 200 Basket Case Project

Post by KarlP »

You've come a LONG way with this bike. Nice job, really.

I think you're main is too big. Juliend is right, it is tricky to get this motor to run clean from idle to WFO. The way I used to do my hybrid was to poke along in third gear at 13 mph. I know it was 13 because I have a Checkmate enduro computer on there. 13 mph is just over idle in third, maybe 1/16 throttle. I'd whack it wide open from there and wanted it to pull clean. Adjusting the air screw really small amounts made surprising changes, you could easily go past the spot that worked best. Keep in mind this is a Ron Black modified carb.
I don't recall ever doing a plug chop on that bike to check the main. Ron sent it with a 150 installed and a 152 spare, I think. It ran fine up top so I left it alone. I don't run around much on the main, anyway, and would much rather have a clean pull from 1/16 throttle.

Using the choke to try to diagnose a jetting question is a questionable practise, IMO.
'08 KTM200xc
'99 CR/KDX Hybrid with that RB stuff done to it
KX100 for the boy
Thrahl
Member
Posts: 222
Joined: 08:51 am May 30 2012
Country:

1989 KDX 200 Basket Case Project

Post by Thrahl »

Alright so this is some of what I have been doing. I haven't had time to just sit down and work on it for hours so I have doing small things (the small things are all that are left really).

First off I replaced the water pump seal. I was getting water in my oil and oil in my water. The old seal looked shot. It was kind of a hassle but needed to be done. Sorry I didn't take any pics.
I bought new grips. The cheapo ones that came with my $20 eBay throttle tore after leaning it on my shed about 5 times. Put some pillow tops on there because I like the look and they come in GREEN!
Image

I also did some painting. I saw a thread a while back about someone painting the KIPS cover green and the letters black, I think it was Slick_Nick. I liked that and am stealing it. :mrgreen:
Image
I haven't filled in with black yet because I used all of my black paint on my frame. I'll finish it later.

Also painted the kickstarter lever because it was really ugly and stuck out like a sore thumb. The main shaft is green and I am going to cover the part your foot sits on with rubber or something because paint would just get destroyed.
Image

Also as I was doing something on the rear end I inspected the chain and look what I found.
Image
There is another too, just a lot smaller and is out of focus in this pic.
Image
I am super lucky I caught this before the chain snapped, it was very very close to breaking and I haven't made a chain guard yet so it would go straight for the cases.

This is an RK 520 roller chain. They are cheap but from everything I have read online they are pretty tough. I haven't even taken the bike on a real ride yet, just testing around the yard and down the street.
According to BikeBandit these have a warranty, though I didn't buy it from BB. Anyone ever try to warranty these chains?

So what's left:
- Rubber pipe mounts
- Rubber pipe/silencer joint
- Chain guard/case saver
- Mess with jetting
- Repair/replace fork seals
- Find and fix small oil leak

And that's about it. The bike should be done and ready to rip after that. Hopefully I will be able to take care of most of that this weekend.
Expect a full photo gallery and video soon.
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 »

Those cheap RK chains last me about 2 years. I like them fine, and don't mind replacing the chain and sprockets every other year.

Bike is looking great. I'm glad you've taken the time to fix her up as nice as you could. This is pretty much the way I built my 89. Money was tight, I did the minimum to get riding, and continued working on it and tweaking it as I could.

As far as the jetting, the issue lies in the design. You have a carb with 3 circuits, and an ICS engine with a nearly 10,000 rpm operating range. It is not possible for the fuel to be metered perfectly for 3,000 rpm 1/4 throttle and 3,000 rpm WFO simultaneously. If you get it rich enough to eliminate that bog when you just crack the throttle open from idle speed, it's going to be much to rich to pull cleanly up top. There is always going to be some measure of "rolling on" the throttle with a carbureted two stroke to maximize acceleration. If the bog is very noticeable, then yeah, you probably need to keep tweaking the jetting. You should be able to get it to a point where you wouldn't ever notice it unless you were trying to.
Image
Post Reply