Opened to rebuild, found piston has broken skirt.

Ok fellows.... Part of the skirt is missing... No where to be seen....


2004 CRF230F

ImageUploadedByThumper Talk1382406934.616440.jpg

Edited by George_ORH

No debris or remnants of it anywhere inside the case so far.

Crank Rod seems to be in great shape (no play or such),

Cylinder wall seems to be clean, 


I will be washing out the case as good as possible and then putting it back together (new pistons and such of course).


I bought this bike not running and was hoping for a clean rebuild.  Maybe I will get it back together and be ok on everything else when I fire it up.


When I purchased it, The muffler had some "slits" in the side of it due to damage.  The muffler had no endcap or baffle.

The carb was still jetted stock.


I imagine the bike ran super lean and ate away at the piston skirt....  I'm sure it disintegrated into oblivion and went through the oil. I hope. 



Let me know any thoughts you guys have on this.



if u cant find the skirt I imagine it was extracted  and then slapped back together ?


the piston looks like hell  LOL


I would be worried about the crank unless your replacing during the rebuild also ?

Ok fellows.... Part of the skirt is missing... No where to be seen....



2004 CRF230F

attachicon.gifImageUploadedByThumper Talk1382406934.616440.jpg




That is a huge chunk of piston missing, it has to be in the bottom end somewhere. I can't imagine a piece of metal that large breaking up and exiting the engine. I would bet that it's still somewhere in the bottom end of the case. How did the head look.? That piston had "excessive" wear, I'm amazed it stayed together with half the skirt missing. I would do a very thorough rebuild going back with it.


Please post more pic's if you find the missing piece. 


Good luck.



I had no plans to replace the crank or crack open the lower end IF I can keep from it. 

Any recommends or ideas on how to get all of this out?


The head seemed clean from what I remember, But I will inspect it a little close and post a photo of what that thing looks like.  I do remember

the valves having a lot of buildup on them (this thing still ran but was BLOWING smoke).


When I pulled the head off, There was "debris" on top of the piston.  Loose Debris.  I couldn't tell what it was exactly, But was just small particles of



Just so everyone knows, I did not drain the nasty oil out of the engine yet... Any bets on what I find in that (or the screen in there)?




Your Throwing your $$ down a rat hole:

1) Catastrophic engine failure.

2) You just bought the bike, so you can only guess on its past history.

3) You can plainly see the lack of

maintenance this bike has had !

4) You have decided to NOT

Disassemble the lower end to closely

clean and inspect all bearings,

Gears and clutch plates?

5) No way possibly to find any metal particles in any of the bearings or cavities right?

6)The engine does not have an externally cleanable oil filter!

Or you could build it correctly the first time and enjoy having trouble free fun for many years to come.


It's always less expensive in the long run to do it right the first time.

Edited by adnohguy

If there was a "like" button on here, I would click it...

I'm slowing down my hurry, and doing it right.

I will do the tear down and then order

The parts I need.

Always good to get a reality check!


Not only is a huge portion of the piston skirt missing, but the skirt that is left has sever wear marks that look like seize marks.


As an absolute minimum, you will need to hone the cylinder. You probably should plan on having the cylinder rebored and get an oversized piston.


[once you decide you need the rebore, you might look at larger pistons that increase the displacement]


My guess is that the bike had a catastrophic lubrication failure. Either by severe over-reving, or failure of the oil pump. Or perhaps worse, some idiot running  it without oil.

I will be checking all tolerances on everything before it goes back together, Cylinder walls, Valves, Etc.

Honing the cylinder with a new piston/ring install is a must Every time.  :)


However, I now have access to another running engine that it looks like I will be buying.  I'm going to either

part out this current motor probably or simply advertise it the way that it is and sell it all together for a decent



I found the piece of skirt last night. It almost fits up to the piston perfectly so that makes me feel a lot

better about everything now.  I had greasy hands or would of snapped a pic from the garage of it, I will

try to get one next time I'm in my garage for every one to enjoy.

I'm slowing down my hurry, and doing it right.

I will do the tear down and then order

The parts I need.

Always good to get a reality check!


Good call !

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