KDXRIDER.NET

Hi all, I hope this the right place for this.

Working on my new to me 92 kdx200 (e):
It was $200, I was told it had compression and a spark. The rest looks a bit abused, and has been sitting, but it has a fmf gold pipe on it, so I went for it.

The engine never turned for me. After some time, tool purchasing, reading, and soaking, I got the cylinder off. The crank case is bone dry, dirty/slightly rusty, and frozen in place.
I have a top end kit on the way (trigger happy purchase finger). Should I just plan on splitting the cases art this point and doing a total rebuild? Or buying a known good bottom end?
Or.. can I soak the bottom end for a few days, work it loose, clean it out, slap it together and ride like there's no tomorrow?

I do mean this as a serious question. I've never split a case before, but just read the writeup on it. I've been on 4 strokes for a good long time, so there are a good bit of design differences here that I'm adjusting to.

Thanks for your words of wisdom..

How did the lower rod bearing feel? check for smooth rotation and and up and down play at the big end bearing

Well so far the crank doesn't rotate, and the conrod won't even move in the way that it should. I've got it all soaking in wd40 to loosen things up, then I'll flush it all out and see how the play feels.

Sounds like you are definitely going to need crank bearings, seals, and a rod kit.

Yeah that's a roasted big end bearing

That's probably a reasonable assessment.
It seems that it was frozen from sitting dry, not from running dry. Cylinder loOKs good, heck even the piston looks good. Piston pin ring was pretty crusty, but the pin pushed out by hand, and the crusty stuff I'm pulling out seems like dried oil with a hint of corrosion.
It's all loose now, rotating freely, very little up and down play in the conrod. I'm bathing it in oil, rotating it around and wiping off the crud that comes out.
I haven't checked the transmission oil yet, but I think I'll stop rotating anything until I know there's something still in liquid form in there.

I dunno guys, this might be a save... hah. What happens when the bottom end bearings go?

Friedom wrote:I dunno guys, this might be a save... hah. What happens when the bottom end bearings go?

I recently finished a rebuild on a kx250 crank and bottom end...the needle bearings were completely flattened and fused to the crank pin. In unlucky cases, the piston will smash off the bottom after the bearing goes...you would notice loss of power / compression and bike dying very quickly and not idling

I'll look a little closer. It looks like some ambient moisture got into the oil puddle in the crank case after it was parked. Thankfully, the piston was about 30° btdc, and the big end and crank bearings are higher than that level. I'm going to take the engine off the frame, but right now the crank chamber is mostly full of diesel to thoroughly slosh out the residue and junk in there.
Then I'll probably use the same fluid to do the main cleansing of the cylinder and other gunk parts.
Pulled an old rats nest out of the air box. The air filter got chucked - was coated and crusty. Inside of it was spotless, though, so there's hope still!
Other than that, I've got tires (trakmaster II), chain(RK), air filter, spark plug, wiseco piston kit, clutch cover seal, left KIPS valve, right radiator and guard, and soon a spark arrestor/silencer on the way. Still on the fence about stock or aftermarket. There's a stock setup on ebay for $70 + s&h. Any reason to go one way or the other? I like quiet. Any concern about not being able to get the material to re pack it?

Man it's hard to build and stay in budget when you see the other build threads on here. I'd be a little concerned with getting my bike as clean as some of yours.
Or rather, riding it when it's that clean.

you say ( very little up and down play in the conrod.) There really should be no up and down movement in the con-rod There should be some side clearance on the bottom end of the rod. If there is any rust at all on the bearing or pitting, it will quickly wear out and when it goes will ruin your new piston and possibly the cylinder. I would split the cases and have a good look at the bearings on both ends of the crank plus the big end bearing. Your crank seals would almost surely be dried out and ready to leak. I don't know off hand what the bearings cost but it would be money well spent to replace them as like I said before the damage they do when they disentigrate we'll not be worth tying to save them.

I see your point. I'm trying to find the line between practical and necessary.

The reason I was vague about the play in the con rod is that I don't have much experience in figuring out the difference between the up and down play and side to side play. How do you have one without the other? What's acceptable? I don't feel it move up and down (I played with it more) when I isolate movement from side to side. Are we talking visible, tangible movement or micrometer movement?

I'll most likely split the cases, I'm in this far. We'll see.

I don’t think you have a choice.

If it’s rusted anything then that part is pitted so you will have rough pitted uneven bearings surface for starters. Now with a lot of perseverance you could free it up which will mean it could go in a fashion even if the shaft is pitted on the seal. This motor in now condemned to Murphy’s rule and is going to blow at the most inconvenient time.
When you take it out have a think about where is the point in this ride that will really piss me of for not listening. That’s when it will blow.

On the other hand what a wonderful opportunity to get to know your new toy in a very intimate way.

Well spoken, sir.

My consideration was that all of the bearing surfaces were above the water line, so even though there is some rust in there, it may not necessarily be in the most important places (bearings, journals, shafts, carriers).
Wishful thinking

first is ignorance, wishful thinking, hindsight, wisdom.

unfortunatly experience teaches

If we're willing to learn from it

if there is rust in the commission chamber, the bearings are toast. they evidenced this by not moving at first.

split the cases, replace ALL the bearings both crank and transmission, and it will be done for a few years worth of riding.

Yup. Pulled the engine last night. Who knows how many years this thing sat. That means I send the crank off to someone for service, right? Any recommendations for crank shaft work, or for which seals and bearings?
I suppose the way to do it is a bottom end kit that covers everything.
I'm excited. And terrified.

Should I start am additional build thread? Just ordered steel kips parts from over the pond..

Thank you everyone for chiming in. I got so many responses, I really appreciate it as I'm new here.
I guess I really didn't want to split the cases, but it shouldn't really be that bad. Just have to stop being a cheap skate.
Anyone have splitter/holder/pullers they want to sell or rent?

Ok, next question: should I plan on new transmission bearings while I'm in there?

If it were me I would. You already have the cases split, do them now and forget about them until the next total rebuild. BTW, when I had my motor apart last winter for new crank seals, had the crank rebuilt, new rod and bearings, and all the bearings inside the cases. Peace of mind.

Dekon wrote:If it were me I would. You already have the cases split, do them now and forget about them until the next total rebuild. BTW, when I had my motor apart last winter for new crank seals, had the crank rebuilt, new rod and bearings, and all the bearings inside the cases. Peace of mind.

Well I don't even have the clutch cover off yet, just the top end.
I've got the crank lined up to to be rebuilt with new conrod and bearings. Have a whole engine rebuild seals kit too, and a wiseco top end. Just wondering what else to order, are there more bearings inside there beyond the transmission and crank?