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Here's a new Piston that I just got done cleaning up all the sharp lower edges and intake port.

Another 220 top end going together. :)

Note : Picture is a little deceiving as it's zoomed in and the chamfer is not that drastic.

Good to see C George.

Some questions if you don't mind as I'm relatively new to KDX's and then only a 200. I will be converting/boring 200 out to 220 but don't have all the parts yet.
The hole looks bigger than the two 200 Pistons I have. Is this normal for a 220?
Plus the hole looks wider than would be needed and be partially blocked by the two stays in the cylinder is that correct or not?.
Did you change the shape?
What brand is that one? It looks thick enough to be forged.
Thanks
Tioli.

Tioli wrote:Good to see C George.

Some questions if you don't mind as I'm relatively new to KDX's and then only a 200. I will be converting/boring 200 out to 220 but don't have all the parts yet.
The hole looks bigger than the two 200 Pistons I have. Is this normal for a 220?
Plus the hole looks wider than would be needed and be partially blocked by the two stays in the cylinder is that correct or not?.
Did you change the shape?
What brand is that one? It looks thick enough to be forged.
Thanks
Tioli.

It's a Wiseco Forged piston. The intake hole in piston is stock size , just chamfered the edges so it may appear larger.
I chamfered and sanded the piston skirts to keep more oil from scraping off the cylinder.

BUT , was any of this needed or nessesary ? NO , Probably not , I just suffer from over thinking ,, ha ha

I just picked up a good 220 top end for a conversion . That may be the cheaper way to go.

BUT then I flaked a section of electrofusion coating off a port by trying remove a sharp edge , so I screwed that one up :( :(

When I got my 200H the piston in it was a ART so presume prox. I was really surprised at how undressed it was. You could see the wear on the skirt where the sharp edges just scraped the oil off and wore down.
I couldent help but just look at it and wonder how they could sell a piston like that. Some thing was wrong either they (big company) know what they are doing or I'm a anal idiot.
The replacement wossner was finished well with chamfers in all the right places. It will be interesting to see how the wossner wears as the coating they have will tell all.

Tioli wrote:When I got my 200H the piston in it was a ART so presume prox. I was really surprised at how undressed it was. You could see the wear on the skirt where the sharp edges just scraped the oil off and wore down.
I couldent help but just look at it and wonder how they could sell a piston like that. Some thing was wrong either they (big company) know what they are doing or I'm a anal idiot.
The replacement wossner was finished well with chamfers in all the right places. It will be interesting to see how the wossner wears as the coating they have will tell all.

Thats pretty much my thoughts and this picture is very deceiving as to hold the piston in your hand " vs highly zoomed in " it just looks like the edges were rounded off.
To each there own but I think it was worth doing. I can't see where it would ever hurt anything.

I also think it would help eliminate the possibility of a cold dry scuff / seizure when using a forged piston .

I've never seen it happen but I guess forged expands quicker than cast and could cause that problem.

Tioli wrote:When I got my 200H the piston in it was a ART so presume prox. I was really surprised at how undressed it was. You could see the wear on the skirt where the sharp edges just scraped the oil off and wore down.
I couldent help but just look at it and wonder how they could sell a piston like that. Some thing was wrong either they (big company) know what they are doing or I'm a anal idiot.
The replacement wossner was finished well with chamfers in all the right places. It will be interesting to see how the wossner wears as the coating they have will tell all.

I have a Wossner in my YZ250 and can tell you when I had my pipe off I looked up the port to check the piston and the coating is gone. Skirts look like a wiseco now. Perfect with no marks but no coating at all. The coating may help stop scuff during break in. Piston has maybe 15hrs. Very nice pistons at only 10g. heavier over stock.

Sending the cylinder out to Millenium for replate and am using this same piston :)

s10gto wrote:

Tioli wrote:When I got my 200H the piston in it was a ART so presume prox. I was really surprised at how undressed it was. You could see the wear on the skirt where the sharp edges just scraped the oil off and wore down.
I couldent help but just look at it and wonder how they could sell a piston like that. Some thing was wrong either they (big company) know what they are doing or I'm a anal idiot.
The replacement wossner was finished well with chamfers in all the right places. It will be interesting to see how the wossner wears as the coating they have will tell all.

I have a Wossner in my YZ250 and can tell you when I had my pipe off I looked up the port to check the piston and the coating is gone. Skirts look like a wiseco now. Perfect with no marks but no coating at all. The coating may help stop scuff during break in. Piston has maybe 15hrs. Very nice pistons at only 10g. heavier over stock.

I'm not a big piston coating fan " personal preference ". I like a piston that is lightly knurled to hold the oil on the surface.

Iv seen Pistons with light grooves machined around the outside all the way up the sides.

Thats how this Wiseco is but much lighter as you can only feel with your finger nail.

Tioli wrote:Iv seen Pistons with light grooves machined around the outside all the way up the sides.

Arias used to make high performance four stroke pistons that way. Not just lightly knurled like this Wiseco 2 stroke
but destinct machined grooves to hold oil.

Worth the bump as I'd highly reccomend when putting a fresh top end together :)

Wait wait; I'm stupid I guess. Why would the skirt ever contact the cylinder? I thought only the rings made contact (separated by an oil film).

The sharp, undressed edge of the skit can shear through the oil film.

doakley wrote:Wait wait; I'm stupid I guess. Why would the skirt ever contact the cylinder? I thought only the rings made contact (separated by an oil film).

Your not stupid , because in the perfect engine world every metal part is separated by oil. Unfortunately we don't live there and some piston rock is inevitable.

david wrote:The sharp, undressed edge of the skit can shear through the oil film.

Exactly :)