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Wanted - used YZ250 piston

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Looking for a 2002 or newer YZ250 piston. I was hoping someone would be willing to donate a used one, not concerned about brand. Doesn't need to be nice, but not wanting one with a busted off skirt or melted crown. I will pay shipping. You can just PM me.

Background -

My 2005 is a bit of a hybrid. Uses a 2000 KTM 250SX rod and 2005 KTM 250SX piston, along with a cylinder spacer. It's a modern version of the mid 90's long rod YZ that was ever so popular.

Anyway, I've always sort of wondered what the differences were between the KTM and Yamaha pistons, so I was hoping to get a standard YZ piston so I could do some measuring and comparing. Also, the KTM doesn't have a boost port window in the skirt like the YZ does, and I am contimplating cutting one of my pistons, although the stock window location might not be what I need anyway.

Thanks!

Edited by adam728

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Where in MI are you located? If you were local, that'd make things easy... (I'm in the north detroit 'burbs)

I have one sitting around (my stock pistion). I got bored one day so I hosed it clean with carb clean, and may have scrubbed it with scotch brite... but otherwise it's whole and just taking up space on the bench.

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I'm in the thumb (Caro). Will be in Troy in about a month (Aug 19th-21st). Otherwise I don't know when I'll be getting down that way.

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If you're willing to pay for the piston itself, I see used ones on ebay all the time. So you may have $20 - $30 into it to your door.

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If you're willing to pay for the piston itself, I see used ones on ebay all the time. So you may have $20 - $30 into it to your door.

I may go that route. I was just thinking with so many in the community here that there are lots of rebuilds happening, and most people just tossing the old piston, that maybe I could find someone willing to send one my way. Really low on my priority list, just thought I'd throw it out there.

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Hey Adam, I have a few if you pm me you addy I'll send a few I don't know why I save them but they are lined up on a window sill. 125,200,250,265, 2504t I prob have ktm's too!

Gary

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I can send you the one I have. Just PM me your address and I get it in the mail. Don't worry about postage... being so close I can probably send it for only a couple bucks.

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Thanks to everyone willing to help. JFielder23 got one to me yesterday.

I'll have to get some pics and measurements up some time. I assumed their was a difference in wrist-pin-to-crown distance between the YZ and SX pistons, but they look identical when lined up on a single wrist pin. There are some other differences, but it looks like I could experiment with actually running a YZ piston in my YZ. 🙂

Or vice-versa, other guys could possibly experiment with a winowless 250SX piston in their YZ engines. I'll know more once I measure them up at work today.

Edited by adam728

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Well that's interesting...

I'm pretty sure the Wiseco single ring YZ250 piston is windowless as well. But I've never been sold on the single ring thing...

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Adam, did you ever get around to doing accurate comparisons of these pistons?  I'm kinda curious about it.

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Yes, then I forgot to post it! I will get the measurements up this weekend, all on my computer. In short, a 250sx piston will work in a yz250.

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This is for a 2003-2006 KTM 250 SX piston. 03 and 04 were single ring, 05-06 two ring. I've ran both in my bike.

 

The biggest difference between the YZ and KTM is the YZ's intake skirt window and cutaways. The KTM skirt is more "standard".

 

Stock YZ piston provided graceously by JFielder23. Wiseco piston for an 05 KTM 250SX

 

Center of wrist pin to top of dome

KTM - 41.94 mm

YZ - 41.99 mm

 

Center of wrist pin to edge of crown. This one I had a stuggle measuring, as both pistons have a small chamfer on the piston edge. Depending where I picked up the edge with the height guage I could easily vary things close to 1 mm. You can see in the 1st pic with both pistons on 1 wrist pin that the height is actually the same down to the chamfer. The YZ has a larger chamfer, which kept coming out ~0.5 mm shorter than the KTM.

 

Crown to intake skirt base

KTM - 75.75 mm

YZ - 70.88 mm

 

Crown to intake skirt base

KTM - 75.58 mm

YZ - 75.42 mm

 

Weight (not sure if a cast or Pro Lite KTM piston would close the gap further)

KTM - 228.8 g

YZ - 215.5 g

 

Basically running a 250 SX piston in a YZ will changes the flowpaths during intake and how the boost port is fed during cylinder filling.

 

 

 

20130719_043614_zps01821de0.jpg

 

20130719_043713_zps503e0b09.jpg

 

20130719_043700_zpsee4be0cb.jpg

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