Bottom end rebuild? (pic heavy)

[Sieg]

The question: Do I need a bottom end rebuild? If yes, should I have a shop rebuild it, or is it to doable for someone with moderate mechanical experience?

Short version: Gas in the transmission, top end in bad shape, shipped off to PowerSeal this morning.

Long version…

Preface: Dirtbike noob. This is my first rebuild.

Background: The bike seems to have been running rich since I purchased it last summer. I had corrected the float level and planned to correct the jetting this spring. I took it on 5 or 6 rides since I bought it. A few weeks ago I took it out for a ride, and it lacked some power. The next weekend, I go out riding again. I kick it over and it starts, but spews out gas/oil all over from the exhaust. I thought that was strange, but afterwards it seemed to be running ok still. About 5 minutes into the ride, I notice oil has been coming out the case breather tube (then hitting the chain and being sprayed everywhere). I start heading back to the truck and I hear clanking. I kill the bike, and carefully try to kick start it, but the kick starter is frozen.

Fast forward to today.

I drain the tranny oil, and it is pure gas/oil. Probably 10 hours of riding prior I had swapped out the oil and it came out normal. What caused this? Leaving the gas on?

I begin the tear down process, and the first thing I notice is severe damage to the case... Was this intentional by someone sick of being patient in splitting the case?

Next up, cylinder head. It looks like it just needs a little cleaning up... right?

The piston looks like someone ran over it in a gravel driveway.

 

[Sieg]

The underside of the piston, cylinder wall, and bottom end just seem to be chewed up.

 

[Sieg]

It seems that there are a lot of metal shavings in the lower end, what caused this? There is some serious wear on the crank assembly.

It's a 1997 KDX220.

 

[IndyMX]

Yeah, If I were the unfortunate owner of that engine, I'd replace everything that moves.. and a few things that don't move....

Complete top & bottom rebuild. Whatever put that nasty gouge in the crank had to have caused other serious damage..

It would be a waste of money to rebuild that top end with a freshly plated cylinder without going the rest of the way with the bottom end.

 

[SS109]

Wow, that is some serious carnage! :whoa:

Personally, I would trash the engine, source another one, rebuild it, and get back to riding. There doesn't seem to be much there that is salvageable IMO.

 

[Joburble]

Wow, that is some serious carnage! :whoa:

Personally, I would trash the engine, source another one, rebuild it, and get back to riding. There doesn't seem to be much there that is salvageable IMO.

I agree.

 

[sr5bidder]

I would not put that engine out just yet, split the cases the proper way look for any other pry marks between the cases (the one in the pic is not in a critical location and should be ok)

the damages look to be caused by the big end bearing coming apart, you can expect scatches in the lower crank case that will need to be smoothed out

your cylinder can be fixed (plated or sleeved)

you may want to buy a used crank to have rebuilt depending on the condition of the crank halves.

what may have happened to cause the oil to be spewing out the case vent is a piece of the lower end smashed through the cranks wall into the transmission area letting pressures blow through, if thats the case it may be cheaper to buy another kdx and part the remainder of your original..

 

[whenfoxforks-ruled]

The screwdriver/BF-pry bar to pry apart cases strikes again! It sure looks as if debris was drawn into the engine at that point? If not, there is another entry point. If the cases can be fixed, the rest can also. A kdx, Fredette or Forward Motion to fix the crank, cylinder and head. All new bearings and seals. piece of cake. Only 1 issue with getting another engine. You could be going down the same road? Maybe just a set of usable cases? What carnage! Thanks for sharing. Vintage Bob

 

[reepicheep]

My KDX rebuild was the first bottom end I ever did, and it went fine. A good learning experience. You will have to spend some time thinking about various steps and doing some research, but ultimately it goes pretty well. Hint... you will need a deep freezer and a BBQ grill for reassembly. I'm serious.

I wouldn't re-use that crank, and that cylinder is going to need to be replaced or sleeved... perhaps it could be bored out and plated. The pry marks on the case aren't a problem, though it does indicate that a previous repair was somebody who was inexperienced and frustrated. Hopefully they gave up before actually getting the case split and sold it to you or took it to a shop, so the scope of their damage is limited.

If you do rebuild it, you will be either paying stupid high prices to Kawasaki, or running around to your local bearing shop for bearings and seals (with the occasional unobtanium part order from Team Green). You will also be running back and forth to Harbor Freight for some new tools like steering wheel pullers and bearing splitters, and various odd long bolts to cobble them together into something that will roughly duplicate the "real tools" for the job. It's all very doable, but time will tick by and you will spend a lot of time working on it.

That's probably the argument for just sourcing another engine. If you can find something on ebay that maybe just needs a top end rebuild that you could buy for $300 or $400, you might not be out much more money and will save yourself a BUNCH of time, and you can keep the old bottom end for parts for future adventures... On the other hand, there is no promise that ebay motor is any less likely to blow up then the one you just crinked. Kind of a "roll the dice and take your chances" kind of deal.

Either way it's totally solvable. Just make sure you like the bike, as you will be into it for some decent money before you are done. If it's the bike you want (it was for me) it's a bargain. If it's not the bike you want, sell it to somebody else cheap and let them restore it and go buy one of the smoking good deals on other dirt bikes out there right now.

 

[reepicheep]

Oh, and thats a mounting boss, so I don't think debris entered the engine from there... though that gap may let water in and ruin the fine steel patina on one of your engine mounting bolts ;).

 

[whenfoxforks-ruled]

Oh, and thats a mounting boss, so I don't think debris entered the engine from there... though that gap may let water in and ruin the fine steel patina on one of your engine mounting bolts ;).

I thought about that also. I would bet the hacks got it apart though, finally and 1 way or another? And double what he said about the green prices on parts, at least if you have to pay retail. Price Service Honda for oem, unless you know a green dealer real good. 20% is only good if its over dealer net, not off retail! Not many shops can survive doing that for everyone. Vintage Bob

 

[dirt bike dave]

Wow, that is some serious carnage! :whoa:

Personally, I would trash the engine, source another one, rebuild it, and get back to riding. There doesn't seem to be much there that is salvageable IMO.

x3.

While it may be a learning experience to rebuild that motor, the cost of parts and repairs make it economically unwise, IMO. You could probably find a complete bike for what it will cost to properly rebuild that motor.

 

[reepicheep]

Hmm...

$50 of so for a gasket kit.
$75 for all new bearings and seals.
$200 for a good used crank.
$50 for various tools and consumables probably not on hand....

So that much so far is $375.

Now for the top end... clean, bore, plate, new piston, small end crank bearing and gaskets... $500.

So you are up to $875, but for a 225 ported big bore. Maybe $775 if you go with a sleeve instead?

I bought a $700 KDX-200... and as you could expect, it needed all new top end. So it wasn't a $700 KDX, it was a $1200 KDX. Except that the rear shock was destroyed as well. And the rear linkage. And the front forks. And the transmission output shaft. And the rear subframe. So it was really a $2000 to $2500 KDX...

That's a lot for a KDX for sure on one hand. But on the other hand, $2500 was "redone top to bottom" to better then new standards. It was worth it to me... its a great woods bike (where I ride) and easy and cheap to maintain over time (I don't ever again want to rebuild a 4 stroke top end).

I have a neighbor selling a nice KDX-220 for $1700... though last I heard he thought he had it sold. So that's a datapoint.

So I guess it could go either way. If you do your own work, and you know your bike is otherwise in very good shape, $800 to $900 is the cheapest KDX you will find.

Or, buy a $1700 good solid runner and just keep your current one for parts for future breakage, or sell it as is for $400 and let them enjoy rebuilding and riding it.

Lots of options. None great, but none a life changing catastrophe either.

 

[julien_d]

I disagree with trashing the motor and trying to find another, or even another bike. I did a complete top and bottom rebuild for under $600. Use ebay to get a good deal on a piston and rod kit, and main bearings and seals. The rest is just time.

Any bike you find for that amount of money is probably going to need a similar amount of work. Good luck finding a used engine that doesn't need rebuilt either, regardless of the disclaimer at the bottom of the for sale ad that says "only ridden around the back yard once", or "fresh top end". :rotfl:

Just do it!

weld/replate cylinder $200
Rod kit $80
crank rebuild labor $50
main bearings/seals $50
Piston kit $100 (wait for a good deal on ebay!)
Gasket kit $50

That should just about do it. There's no reason to trash the crank. A crank rebuild will replace the pin, con rod, and big/small end bearings. It will be plenty good enough after that, and certainly better than somone elses used crank.

J.

 

[jonooffler]

I would say two tubes of JB weld and some wet and dry paper around £15.00 ;) .
For my money I would rebuild the engine you have. I have bought engines before only to find that when you start looking at them, you do a full rebuild the replacement engine, so you end up paying for a second hand engine and a full rebuild. Then you notice the frame could do with a re spray, fork re build ,shock re build new plastics, new spokes ,Chain sprokets the list goes on. Some times it's better to call it a day and just get a newer bike .
Only to find that the piston needs to be changed ..................... :bang:

 

[Joburble]

That cylinder looks munted (stuffed, ruined). Even if you get it bored, sleeved, plated or whatever, it looks like some monkey has been chewing on the ports with a dremmel. Nothing like sharpening those port edges up eh! Sharpening port edges (in my understanding) means the guy who did it doesn't know what he is doing. Subsonic air flows better over a rounded surface not a sharp edge, all air flow through the ports is subsonic. Someone who is a retired aerospace engineer (Mudpack) may have to correct me on this one, but that is my understanding.

 

[dirt bike dave]

I don't see how you can rebuild that crank. It's missing peices. It's toast.

The cylinder is toast. The crank case halves may be toast.

Piston is toast.

Head can probably be saved, but will need some attention.

That's what happens when you have bits of bearings and crank flying around in there.

Ballpark, it's going to be $200 for a crank assembly, $120 for piston, wrist pin bearing and rings, $60 for crank bearings, $75 for a gasket set, $50 for misc. seals, $200+-?? for a cylinder. That's over $700 right there, not counting crank case halves (if you need them), shop labor, your time, misc. unforseen issues like damaged KIPS valves, etc...

Unless the rest of the bike is flawless (doubtful, seeing those gouges in the crankcases), I'd part it out and use the proceeds + the $1,000+- you will save by not rebuilding this one for another bike. JMHO.

 

[whenfoxforks-ruled]

That cylinder looks munted (stuffed, ruined). Even if you get it bored, sleeved, plated or whatever, it looks like some monkey has been chewing on the ports with a dremmel. Nothing like sharpening those port edges up eh! Sharpening port edges (in my understanding) means the guy who did it doesn't know what he is doing. Subsonic air flows better over a rounded surface not a sharp edge, all air flow through the ports is subsonic. Someone who is a retired aerospace engineer (Mudpack) may have to correct me on this one, but that is my understanding.

Yes, that cylinder is junk. It will likely never be able to jet, much less run anywhere close to proper. I did not see the hopefully grade school attempt at screwing up the ports. The old cheap electric hobby dremel strikes again! And I do not believe even Eric Gorr could fix that, the material removed needs to go back. I went through 4 CR250 heads till I found 1 that would actually work. A new 1 would have been less. A good used crank? Lots a luck with that, or just ride REALLY slow! Anything used should be inspected carefully with measuring tools, and a little by eye, or rebuild it and forget about it for a while. Vintage Bob

 

[_JOE_]

That cylinder looks munted (stuffed, ruined). Even if you get it bored, sleeved, plated or whatever, it looks like some monkey has been chewing on the ports with a dremmel. Nothing like sharpening those port edges up eh! Sharpening port edges (in my understanding) means the guy who did it doesn't know what he is doing. Subsonic air flows better over a rounded surface not a sharp edge, all air flow through the ports is subsonic. Someone who is a retired aerospace engineer (Mudpack) may have to correct me on this one, but that is my understanding.

Looks like some 8th grader did that in shop class or something.

 

[_JOE_]

This seems like a kick in the nuts after buying a KDX, it's usually an RM125 that looks like that....... ;)

 

[sr5bidder]

O.P (sieg) seems less interested than the rest of us ..

I agree w/ julien_d on all counts except 2.. 1) inserting a sleeve instead of repair/replate.. by the looks of the cylinder it would run much more than the quoted $200 to weld and replate, and 2) "That should just about do it" ..there is always more, and I hold firm to the idea that the case is more than likely blown out between the crank area and transmission area(remember the O.P stating that oil was blowing out of the breather) there is little room for anything besides the crank halfs in there

 

[Joburble]

Good point sr5bidder, so you are saying that something that fell into the crank area may have punched a hole into the gearbox area, correct?

Oh, and if I was sieg I would feel too ill to post too.

Nice to see that someone who posts a question gives such good info and good photos. Sorry about your motor sieg. Be comforted in the fact that it's just a motor not a body part, I would swap a bad motor for my bad knee anyday.

 

[dirt bike dave]

I agree there is certainly a hole between the crankcase and the gear box, and pressure forced the tranny oil out the breather tube.

IMO, the usual culprit for causing a hole in the crankcase is excess rod play when the big end bearing fails. The loose rod probably damaged both crankcase halves.

BTW, the crankcase halves are already pitted in the photos, due to damage from the bearings and crank pieces. The cases are either going to be expensive to repair, or they must be replaced. This is going to add hundreds of dollars to the bill if he chooses to rebuild this motor.

 

[julien_d]

Got my cases on Ebay for $75 shipped ;) Didn't feel like fooling with trying to weld the crack back by the kickstart assy.

At any rate, everyone is right, it's going to be one nasty rebuild. Maybe I'm an idiot, but I'd be rebuilding what I have before taking a chance on buying someone else's junk.

As for the replate vs. sleeve, I guess it depends on who you know. I got a "spare" cylinder I had welded and replated for $200 total, and it looked just as trashed as this one. I expected to hear back that it could not be fixed. Retail price would have been about 250, or so they said.

Pretty much the only parts in my engine that are the same as when I picked the bike up is the transmission gears and crank ends. It really wasn't that bad. I have right around $600 in the engine.

J

 

[Sieg]

O.P (sieg) seems less interested than the rest of us ..

Absolutely not. I've been refreshing this page on my droid at least every 2 hours since I originally posted. I'm extremely interested in getting the input from the members on here.

Good point sr5bidder, so you are saying that something that fell into the crank area may have punched a hole into the gearbox area, correct?

Oh, and if I was sieg I would feel too ill to post too.

Nice to see that someone who posts a question gives such good info and good photos. Sorry about your motor sieg. Be comforted in the fact that it's just a motor not a body part, I would swap a bad motor for my bad knee anyday.

Yeah, I've had a little :bang: reaction since I first started tearing it down last week. At the end of the day you're right, it's an old bike and I knew the risks getting into it.

At any rate, everyone is right, it's going to be one nasty rebuild. Maybe I'm an idiot, but I'd be rebuilding what I have before taking a chance on buying someone else's junk.

I've really enjoyed your input. I'm not going to completely abandon this motor. In reality I don't have the time for a lot of riding this summer as I'm finishing up my last semester of school, so my plan is to tear the case apart and see how bad it is in there.

My top end is currently on it's way to PowerSeal, so we'll see what they have to say about it when it gets there :think: I may have them hold off on the work until I get the bottom end apart.

One thing that I really don't understand is what's going on inside the bottom end. Is the oil in the transmission under pressure while the bike is running? So if there was a hole between the two cases, would both cases become pressurized and that's why gas/oil would have been spewing out the breather?

As far as cost, I do some side work for a Western Power Sports dealer, so I can get cost on any stuff they distribute... I don't know how many parts I'll need from them, but every little bit helps. The tools is what's killing me. Buying a few hundred $'s in tools that I'll only use a couple times isn't my idea of an investment.