Composite Flaking?

[Gage]

First post Hi everybody. I'm not sure where to start. So Ive been rebuilding a 1989 KX500, I had just gotten through rebuilding the top end with a fresh bore, new Wiseco piston and a 1mm head gasket. As a newbie mistake I put the head gasket on up side down so it started to leak Immediately after I started it up. So I tore here back down again and I'm now waiting on a new head gasket (normal gasket now). I started to look at the piston through the exhaust port and noticed it wasn't as smooth as it once was. So I took the entire jug off and this was what I found. I researched it a bit and Im still not sure where to go from here. Im assuming the piston is alright the way it is or not? What caused this? Was this from the head gasket or something else? Dirt? Im really bummed out right now..   

[Foxx4Beaver]

Looks like dirt evidence...how much time is on that top-end?
Was the filter clean?...is there any signs of dirt in the air boot that got past the filter?...was the motor in the cradle/frame when you put it back together?...dirt from the frame could've fallen right in there while you where putting it together....reason why I always pull the motor to do any kind of internal work.

[Gage]

Like 25mins max. Brand new K&N filter. No I put it together outside the frame. I flushed the motor with Diesel before hand too.

[Gage]

Some one told me that I should have cleaned the new piston before I put it in there with soap and water? Due to flakes from the factory along with cleaning the bore. Though I cleaned the bore.

[Foxx4Beaver]

Yeah,whoever told you that is correct,and just as importantly you want to check for burrs on all the edges.It looks like some kind of foreign matter got in there for sure...how's your cylinder bore look? 

[Gage]

Ugh...Didnt know that... crap. The jug looks about the same as the piston.... Recommendations?

[Foxx4Beaver]

well,going by what I can see in the pics,it does'nt look that bad...but without actually seeing it's kind of a gamble to say go ahead and use it without knowing if anything else is wrong..I know the wiseco that was in my 500 when I bought it,was in ALOT worse shape,it had alot of blow-by and one big deep groove on the intake side....but it got me through a season until I was able to rebuild the whole thing.

If it were me....I'd probably buy a new piston,only because you said it has a fresh bore....do some research on here about Wiseco though ...they're not as good as they once were.I'm running a Wossner,and knock on wood...have had great luck so far.

[Gage]

Thanks mate. I guess I'll test my luck out with this one and see how long it last. At least I know that now, owell.. Hopefully nothing else bad happens. Crossing my fingers....

[Foxx4Beaver]

It'll probably be ok for quite awhile...just be sure to CLEAN the snot out of everything,and check that piston out real good for any loose debris/aluminum filings.I've seen worse,and I've ran worse.
Good luck!

[jonny500]

piston and cylinder tolerance . is the cylinder nikasil or steel. remember a forged piston need a larger tolerance. have the ports been chamfered properly

[DoldGuy]

Gage,

That piston looks like it was washed down (coolant leaking into the cylinder) which will wash away the fuel from the piston leaving no oil to lubricate itself. Before reassembly I would flat plate the head to confirm it is perfectly flat as every KX500 head that I have checked have been warped (some much worse then others). If the piston rings are not "Pinched" in the ring grooves, you can probably have the piston coated & install a new set of rings & be okay, also make sure the cylinder does not have any aluminum transfer from the piston.

I have used these guys with positive results:

http://swaintech.com/why-coat-a-two-stroke-piston/

Hope this Info helps,
DoldGuy

[Foxx4Beaver]

Gage,

That piston looks like it was washed down (coolant leaking into the cylinder) which will wash away the fuel from the piston leaving no oil to lubricate itself. Before reassembly I would flat plate the head to confirm it is perfectly flat as every KX500 head that I have checked have been warped (some much worse then others). If the piston rings are not "Pinched" in the ring grooves, you can probably have the piston coated & install a new set of rings & be okay, also make sure the cylinder does not have any aluminum transfer from the piston.

I have used these guys with positive results:

http://swaintech.com/why-coat-a-two-stroke-piston/

Hope this Info helps,
DoldGuy

That's a good possibility....one way to tell if it was from coolant leaking,is to look at the top of the piston.If it has any white residue on there(from the water cooking),well there you go.

[Gage]

I dont believe its ported. I dont see any whiteness on the top of the piston either. I think DoldGuy might be right though, Im going to take the head to some one who knows a little more than I do tomorrow. The head gasket will be arriving tomorrow or next. Also if I was to run it the way it is now vs coating the piston, what Am I risking? I mean I would hate for it to get messed up again because of how new I am to this then be down money for that too. I'm not racing this or anything, but I dont want it to run like back yard trash.   

[Foxx4Beaver]

have the cylinder checked for flatness too....a perfectly flat head will be useless on an un-flat cylinder

[sandblaster]

Looks like a water problem to me as well.
Just curious, you didn't mention if you measured your crank side play with a feeler gauge.
If you didn't or don't remember what it was, now would be a good time to do it.
Also, with the stator cover off, grab on to the fly wheel and see if you can pull it up or down at all.