KX250F Piston help (newbie)

Gandorlf
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Gandorlf
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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slowgti
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slowgti 4/21/2017 5:48pm
4/21/2017 5:48pm
Why don't you just order a stock piston?
Gandorlf
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Gandorlf 4/21/2017 6:12pm
4/21/2017 6:12pm
slowgti wrote:
Why don't you just order a stock piston?
Because I don't know who manufactures the OEM pistons for my bike.
ed921reyes
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ed921reyes 4/21/2017 6:34pm
4/21/2017 6:34pm
Gandorlf wrote:
Because I don't know who manufactures the OEM pistons for my bike.
pure gold!!!
Jrewing
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Jrewing 4/21/2017 6:41pm
4/21/2017 6:41pm Edited Date/Time 4/21/2017 6:42pm
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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xnationalwrench 4/21/2017 6:55pm
4/21/2017 6:55pm
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..
Jmicmoto13
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Jmicmoto13 4/21/2017 6:57pm
4/21/2017 6:57pm
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 etc. I...
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.
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.
moto314
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moto314 4/21/2017 6:57pm
4/21/2017 6:57pm
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.
beamer
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beamer 4/21/2017 6:58pm
4/21/2017 6:58pm
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??
Jrewing
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Jrewing 4/21/2017 8:55pm
4/21/2017 8:55pm
Alright alright...

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

I need a nap after that. Pizza would be good too
jaredkeller96
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jaredkeller96 4/22/2017 12:04am
4/22/2017 12:04am
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
sgrimmxdad
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sgrimmxdad 4/22/2017 4:28am
4/22/2017 4:28am
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.
imoto34
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imoto34 4/22/2017 4:36am
4/22/2017 4:36am
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.
CLT809
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CLT809 4/22/2017 4:58am
4/22/2017 4:58am
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.
Sixeightone
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Sixeightone 4/22/2017 7:00am
4/22/2017 7:00am
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.
Braap19
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Braap19 4/22/2017 10:32am
4/22/2017 10:32am
I run je Pistons in all my kawis. Great Pistons
Gandorlf
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Gandorlf 4/22/2017 7:35pm
4/22/2017 7:35pm
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 Piston...
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.
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!
Gandorlf
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Gandorlf 4/22/2017 7:36pm
4/22/2017 7:36pm
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 etc. I...
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.
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 Mountain and type...
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.
Haha I expected a few idiots to comment! Exactly what I did thank you Smile

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