KX250F Piston help (newbie)

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4/21/2017 5:34 PM

Hello everyone!

I have decided it is time for my bike (2009 KX250F) to get a new piston and get all the valves re-shimmed etc.

I am sourcing the Piston myself, I hear Vertex is a good brand to buy. My question is I get puzzled by compression ratios and sizes etc, basically I want a stock piston that is the stock compression ratio. Nothing high performance or anything like that! Figured Vital is the best place to ask. thank you.

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I used to think I was indecisive, but now I'm not too sure.

4/21/2017 5:48 PM

Why don't you just order a stock piston?

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4/21/2017 6:12 PM

slowgti wrote:

Why don't you just order a stock piston?

Because I don't know who manufactures the OEM pistons for my bike.

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I used to think I was indecisive, but now I'm not too sure.

4/21/2017 6:34 PM

Gandorlf wrote:

Because I don't know who manufactures the OEM pistons for my bike.

pure gold!!!

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4/21/2017 6:41 PM
Edited Date/Time: 4/21/2017 6:42 PM

slowgti wrote:

Why don't you just order a stock piston?

Gandorlf wrote:

Because I don't know who manufactures the OEM pistons for my bike.

ed921reyes wrote:

pure gold!!!

Haha. I know for a fact it's not Honda

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4/21/2017 6:55 PM

It used to be most all OEM pistons from Japan was manufactured by ART, and you can purchase those from your local dealer or many mail-order shops..

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4/21/2017 6:57 PM

Gandorlf wrote:

Hello everyone!

I have decided it is time for my bike (2009 KX250F) to get a new piston and get all the valves re-shimmed ...more

Don't listen to the ass clowns man. They don't have the decency to simply try and help. Just go to Motorsport or Rocky Mountain and type your bike model in and it will give you OEM sized pistons from various manufacturers. Vertex is a good choice.

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4/21/2017 6:57 PM

I think stock compression ratio is 13:1. I'd go ProX if you just want a cast replacement, JE, CP, or Wiseco if you want a forged piston. Not sure what your confusion is on the size. I assume you just want stock bore size? Sorry I don't know too much about Vertex 4-stroke pistons.

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recmx.com

REC MX, JE Pistons, Wiseco, Rusk Racing, Yoshimura, FXR, Art of War, Dubya, Asterisk, CCR Sport, ZMax

4/21/2017 6:58 PM

Fuck you guys are losers he's asking a very simple question to which you could have simply said " Go to your local dealer and order a stock piston for your year and model stock bore, not oversized. Or simply go online and order the same as above listed or a
Wiseco or other aftermarket brand, again stock bore not oversized. "

What are you guys, like 13 years old??

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4/21/2017 8:55 PM

Alright alright...

GO TO A KAWASAKI DEALER AND ASK FOR THE STOCK PISTON.

I need a nap after that. Pizza would be good too

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4/21/2017 9:46 PM

Wiseco.

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well we ain't the smartest folks in the world...i mean we're fucking dirtbike riders for christ sakes.- BobbyM

If you chose not to decide you still have made a chioce.



4/22/2017 12:04 AM

Get a moose piston, manufactured by CP Carrillo inc, with moose etching on it...cheaper than the one that doesn't say moose but exact same piston

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IG @jaredkeller96

4/22/2017 4:28 AM

Are you sure this is the first time a piston has been put in the bike? If so I would go OEM. If going aftermarket Vertex is a good choice for the kawi's.

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2023 YZ450 OTW
2022 CRF450
2022 YZ125
2016 YZ250F
2015 YZ250F
2008 CRF250R
2001 CR250R
2010 YZ250
2012 CRF150R
2009 YZ125

TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



4/22/2017 4:36 AM

Gandorlf wrote:

Because I don't know who manufactures the OEM pistons for my bike.

ed921reyes wrote:

pure gold!!!

Jrewing wrote:

Haha. I know for a fact it's not Honda

If I was to bet, you don't have a clue who manufacturers the piston for that bike.

To the OP - go to a local shop and have them order you the correct parts. Some brands factory replacements aren't the same and can be MM's off.

Or ideally have the one doing the work order all the parts. And WATCH the work being done if you can, it is easy stuff once you learn.

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4/22/2017 4:58 AM

Performance wise, the stock piston is great in that bike, very "free revving". Unfortunately they are prone to cracking, so on my kx250f's that I practiced on I ran forged pistons.

Stock compression on that motorcycle is 13.2:1, I was kind of surprised when I used high compression pistons on the kx250f's, where most 250f's feel like they just gain bottom end, the kx seemed to pull longer up top with a higher compression ratio. Purely seat of the pants feel, never dyno-ed.

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4/22/2017 7:00 AM

What you need to do is measure the Outside Diameter of the piston with a Micrometer Or a Vernier Caliper. I looked up a Vertex Piston Kit for you. I used a Median Measurement on the Piston size 76.96 with 13.5:1 Compression. The parts unlimited part number is "0910-1806" MFG #: "23259B". Any local Dealer should be able to supply you with that kit. If your piston measures different let me know I can find the part number you need.

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Tony Alessi, "I think it's time to have more kids so I can have hopes of actually raising a champion."

4/22/2017 9:31 AM

From Motosport.com

Pro-X Piston Kit: https://goo.gl/6mS7qQ
Vertex Piston Kit: https://goo.gl/kaBDYH
Wiseco Piston Kit: https://goo.gl/SISKjm

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"Sorry Goose, but it's time to buzz the tower."

4/22/2017 10:32 AM

I run je Pistons in all my kawis. Great Pistons

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4/22/2017 7:35 PM

Sixeightone wrote:

What you need to do is measure the Outside Diameter of the piston with a Micrometer Or a Vernier Caliper. I looked up a Vertex ...more

Thanks a lot. This really helped!!

I've ordered a vertex piston kit along with gaskets etc. So I'm all set! Thanks to everyone with actual suggestions. I knew Vital was the place to ask!

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I used to think I was indecisive, but now I'm not too sure.

4/22/2017 7:36 PM

Gandorlf wrote:

Hello everyone!

I have decided it is time for my bike (2009 KX250F) to get a new piston and get all the valves re-shimmed ...more

Jmicmoto13 wrote:

Don't listen to the ass clowns man. They don't have the decency to simply try and help. Just go to Motorsport or Rocky ...more

Haha I expected a few idiots to comment! Exactly what I did thank you smile

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I used to think I was indecisive, but now I'm not too sure.