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Pro X Piston Kit

Fits Your MachineDisplaying parts for your 2004 YAMAHA YZ250
Pro X Piston Kit Standard (66.36 mm)
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Pro X Piston Kit Standard (66.36 mm)

Fits: 2004 YAMAHA YZ250

Part# 1288530057 | Mfg Part# 01.2321.B

Our Price: $77.59

MSRP: $117.12 - You save $39.53 (34% off)

Get $2.33 in Quick Cash

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5+ In-Stock

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Additional Videos

How To - Rebuild A Top End

How To - Check Piston Ring End Gap

Pro X 4 Stroke Piston

Pro X 2 Stroke Piston

How To - Four-Stroke Top End Rebuild (Part 2)

How To - Rebuild Motorcycle or ATV Top End (Part 2)

How To - Hone A Cylinder

How To - Rebuild Motorcycle or ATV Top End (Part 1)

How To Measure Your Dirt Bike's Piston To Cylinder Wall Clearance

RM YouTube Channel
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Details

    If you’re looking for a cast piston that runs like a top and slides like it’s on ice, pick up a Pro X Piston Kit for you bike, UTV, or ATV.

    Pro X pistons are the premier cast piston made from a specialized low-expansion, low-friction aluminum alloy, commonly used by Japanese OEM engine manufacturers to give the piston an incredibly low co-efficient of friction. For you, this translates to a cast piston perfect for 2 strokes and 4 strokes that has the durability of a forged piston but at a much lower cost. Certain models come with a tin-based skirt coating that reduces wear during and after the wear-in process. This black coating also comes in handy during engine servicing since any excess wear to the piston skirt or cylinder wall will be very apparent in the wear patterns of this coating.

    Pro X uses the best materials available along with innovative designs to give you pistons that are tailor made to the unique requirements of your machine. So if you’re worrying about Pro X Piston Kits being a good fit for you, don’t. Pro X has you covered.

    Specs:
  • Kit includes piston, piston rings, wristpin, and circlips
  • Does not include wristpin bearing for 2 strokes
  • High silicon content aluminum alloy piston
  • Some models include tin-based anti-friction skirt coating
WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

Pro X Piston Kit Reviews

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WRITE A REVIEW
4.5 / 5.0
191 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Star
144
25
9
3
10
Value
4.7 / 5
Durability
4.5 / 5
Fitment
4.7 / 5
Performance
4.7 / 5
Recommend it?
Yes (106)
No (7)
Value
3 / 5
Durability
3 / 5
Fitment
3 / 5
Performance
3 / 5
Recommend it?
No
Garbage
Vetted piston clips are so bad it’s not even worth the headache. Buy the piston; throw the clips out and head to slavens racing to buy the ez clips.
May 5, 2020
East Ford , CT, US
Age: 15-24
Purchased
10 months ago
Gender:
Male
Weight:
161 - 190 lbs.
Height:
5'10 - 6'0
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
No Worries
I had a loud "clicking" sound so I purchased this kit. It solved the issue and have many riding hours with NO issues. Two thumbs up.
April 30, 2020
Statesville, NC, US
Purchased
over 2 years ago
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Quality product
Has all the same markings as my oem piston, great value
April 27, 2020
Edmonton, AB, CA
Age: 15-24
Purchased
2 months ago
Gender:
Male
Weight:
161 - 190 lbs.
Height:
5'7 - 5'9
Value
5 / 5
Durability
4 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Exact fit
Bought this piston kit to try out. Exact size, and fits as described. Much better value than Slavens vortex kits.

-m-2018 BETA 300 RR--
OEM piston and new piston
OEM piston and new piston
March 14, 2020
Calgary, AB, CA
Age: 25-44
Purchased
6 months ago
Gender:
Male
Weight:
161 - 190 lbs.
Height:
5'7 - 5'9
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
So far so good
Fitment and everything was great. No complaints. As long as it continues to perform I dont see any problems. Wish they would include the wrist pin bearing with this kit though. Almost missed ordering that separate which would suck.

-m-1998 HONDA CR250R--
February 25, 2020
Shelley, ID, US
Age: 25-44
Purchased
9 months ago
Gender:
Male
Value
5 / 5
Durability
4 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Great product
Great quality for a cast piston! Definitely recommend on a budget.
February 5, 2020
Anderson, SC, US
Purchased
4 months ago
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
OEM quality
Pro X is my go-to aftermarket supplier. Most are made in Japan and are a supplier to OEMs
January 7, 2020
Battle Ground, WA, US
Age: 45-64
Purchased
10 months ago
Gender:
Male
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Perfect
Fit just right kx65 running like a champ , good product to kids be running hard for weeks now
December 26, 2019
Manor, TX, US
Age: 45-64
Purchased
5 months ago
Gender:
Male
Weight:
161 - 190 lbs.
Height:
5'7 - 5'9
Value
5 / 5
Durability
1 / 5
Fitment
1 / 5
Performance
1 / 5
Recommend it?
No
Only ProX product that sucks
I typically only use Weisco pistons, but thought prox products have been almost exactly the same as the OEM and for the price how could I pass up this piston.

Just to preface my comments, I've done hundreds of top ends.

The piston seemed to be a good quality and I really couldn't tell much difference between the Weisco and ProX. I did notice that the ProX lacked the same level of skirt coating that Weisco has which helps reduce the wear on the cylinder wall.

When inserting the ProX piston into the cylinder it went in super easy and that concerned me. The Weisco always seems to require a little more work to finesse it into the cylinder. I always coat the cylinder with engine oil prior to install so it's not a dry fit. First start with new piston the bike was angry and didn't want to start. Had to kick it 20+ times before it finally started. Yes, the timing was dead nuts on!!

First ride with the ProX I felt like the bike was lacking torque so obviously the compression was low. On difficult hill climbs and obstacles the bike kept dying on me. After about 3 rides I started to notice some piston slap so I immediately turned it off. Looked at the oil level window and there was way to much showing in it. Oil pressure wasn't there!

Went home and ordered the Weisco piston. Pulled the ProX and it looked okay and there was some wear on the cylinder walls where the skirt rubbed, but no damage. Installed the Weisco and it did require a little finesse and fit very tight in the cylinder unlike the ProX. Bike kicked over in 8 kicks unlike the 20+ with the ProX. Oil pressure is perfect and great compression is back! Bike runs like brand new and pops wheelies with ease. Hills and obstacles are no problem again.

-m-2007 KAWASAKI KX450F--
December 10, 2019
Scottsdale , AZ, US
Age: 45-64
Purchased
1 year ago
Gender:
Male
Weight:
221 - 250 lbs.
Height:
6'4 - 6'6
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Best bang for the buck
Great piston and packaging directions a toddler could comprehend and great price

-m-2001 YAMAHA YZ250F--
User submitted image
User submitted image
December 8, 2019
Nashua, NH, US
Age: 25-44
Purchased
6 months ago
Gender:
Male
Weight:
161 - 190 lbs.
Height:
6'1 - 6'3
Show more
Rocky Mountain ATV/MC gift card Each question or answer submitted enters you into a:
$100 gift card monthly drawing and a
$500 gift card quarterly drawing!
Start typing your question and we'll check if it was already asked and answered. Learn More
Browse 30 questions Browse 30 questions and 66 answers
Is the pro x piston a forged or cast piston?
JOHN D on Dec 25, 2016
BEST ANSWER: This is a cast piston.
How do I know if I need new piston?
Richard M on Feb 11, 2018
BEST ANSWER: 1.Pitting/damage to top of piston, 2.scoring/gouging/damage to sides , 3.mics out of bore tolerance, 4.sleeving or overboring cylinder
What is a or b piston kit. Mean for pro-x????
A shopper on Aug 20, 2016
BEST ANSWER: Hey there,

The manufacture measures the bore from the factory and provides a letter to represent the size. For example, "A" would be smallest within the manufactures tolerances and "B" or "C" would be larger sizes. The manufacture will usually stamp the cylinder with the size. The recommendations I received are to go up one letter to account to wear and tear. However, that's not official, just a recommendation that was given to me.
I have a 2002 kx 85 with a ported and polished cylinder. Would this work?
A shopper on Mar 3, 2019
BEST ANSWER: As long as your cylinder hasn’t been bored passed standard piston size yes you can. If your cylinder exceeds stock bore size you’ll need to purchase a piston size that matches your bore size. If it’s stock besides the port & polish your good 👍🏻
I have a rm85 with a locked kick start I'm jus trying to find what could it be ?
shaun w on Aug 22, 2017
BEST ANSWER: If there is metal in the transmission oil you will need to take the right side cover off and see what is stopping the starter lever. if the piston is seized in the cylinder, the top end will need to be removed and repaired as needed.
is this piston a double ring or single ring piston. i have a 2002 YZ125, and want to know if this will be a good fit?
Vincenzo G on May 16, 2019
BEST ANSWER: for 125 it should only be a single. Just replaced and was only a single ring on this design
Does your Pro X Piston Kit come with a Wrist Pin and Wrist Pin Bearing?
Jeremy T on Feb 7, 2018
BEST ANSWER: yes but i recommend purchasing the oem bearing, the difference in quality is clearly visible
I have a 2015 yz250f and I believe the owner before me put a pro x piston in it and it’s time for some rings but need to confirm if it’s a prox piston or not is there any marking on the piston that I can use to confirm that it’s a prox? and if so can I run oem rings or do I need the prox rings?
Nickolas A on Oct 29, 2019
BEST ANSWER: I would never tear down an engine and just change rings. I’ve had a piston break before and the damage it caused was catastrophic. Send the extra money and have piece of mind
I need to change the Piston rings but i only find the full Pro X piston kit. Do you sell the Pro X Rings or does the OEM piston rings work in this case for the Pro X piston?
Angela Monica G on Sep 4, 2019
BEST ANSWER: I would be happy to look into this for you. What is the year, make and model for your machine?
Would this be legal for Ama stock class racing?
Corey G on Mar 17, 2019
BEST ANSWER: Yes as long as it stays in that class engine size. If you get a big bore Set you would have to run in and open class.
I am planning on ordering this kit for my 2000 ktm sx250. This kit doesn't come with the wristpin bearing , correct? Will the specific piston for my bike come with the black coating around the sides or not for my specific bike??
Brian P on Feb 24, 2018
BEST ANSWER: No wrist pin bearing or black coating on the kit for my 250 exc
What to do when blown motor?
Randy G on Dec 14, 2017
BEST ANSWER: If it’s the top end you can have it bored and sleeved, if it’s the bottom end they can be rebuilt but it is time consuming and slightly costly.
Should I hone (with ball hone) my 2009 KX 65 bore before installing the piston? The service manual I have says do not hone, but I see on forums people hone their bores
John F on Feb 22, 2019
BEST ANSWER: John, the best way would be to use a green scotch brite pad. You basically want to remove the carbon so rings seat in well. Hope that helps in you installation. Jeff
Hi, I bought this piston for my 2013 crf250r, it has a dot on it, which way does the dot go it’s very hard to tell?
Corey F on Feb 21, 2019
BEST ANSWER: Dot should be exhaust side, but look at the top of the piston The moon shaped cuts in the piston are to clear the valves, the Intake valve are much bigger Than The exhaust. The smaller reliefs face exhaust side
does it come with the lubrication holes drilled?
Mike n on Feb 21, 2019
BEST ANSWER: No, you have to drill them but it does have instructions on where to drill.
What is standard bore size for a 2001 125 yz ?
A shopper on Jun 22, 2017
BEST ANSWER: Stock bore size on yz 125 is 53.94mm. Check ring gap per manual. If it is offered go with a B size since your bike is old you'll have a tighter fit.
Will this fit 06 crf 70?
A shopper on Mar 20, 2020
BEST ANSWER: To see if this part will fit your machine please enter the make, model, and year into our "Choose a vehicle" drop down boxes found above the product image. If your machine is not listed, we may not carry the right item for your application.
I purchased the prox piston for my 00 yz125. Is the ring omnidirectional? I looked all on the ring and could not find any markings.
Justin R on Sep 22, 2019
BEST ANSWER: The rings can go either way on that application.
Is this goin to fit my beta right is it an a b or c?
sam n on Aug 3, 2019
BEST ANSWER: It would be considered a “b” piston
I have a 2004 KTM 300exc and it’s says it’s a 71.95mm Is it correct and what else’s would I need to finish a fresh top end?
Ethan A on Jul 20, 2019
BEST ANSWER: I used this on a KTM 50cc, so I don know about your size. I would buy a $8.00 digital caliper from Harbor Freight to measure your piston. You probably only need a top end gasket kit to finish. I would also order a couple extra circlips because its easy to loose or ruin them.
Hello, just cheking if this part is for 2 stroke YZ250X 2016? , because the picture has both 2 and 4 strokes piston. thanks
Luis A on Jul 9, 2019
BEST ANSWER: Yes, the picture is just a generic. However, your machine is listed to fit.
I need piston prox size B Ford 2009 ktm 300.
you have it available?

I need piston pro x B d'Or 2009 ktm 300.you have it available?

.thank you
A shopper on Nov 14, 2018
BEST ANSWER: I checked into this for your and this is a size B piston for your machine.
will this piston work in a 2013 Husaberg te250?
A shopper on May 28, 2018
BEST ANSWER: Yes, you will just need to enter in your machine in the drop down boxes above the product image.
How come it doesn't give me the options for a kx100 ?
A shopper on Oct 7, 2017
BEST ANSWER: Unfortunately, we do not carry this piston kit for your machine. If you let me know what year your KX100 is I can check our inventory for you.
will this piston for my 2004 suzuki eiger LTF400F?
A shopper on Aug 7, 2017
BEST ANSWER: Unfortunately, we do not carry this piston for this machine.
It is compatible with the motorcycle KTM 250 EXC-F 2013?
Luis V on Apr 20, 2017
BEST ANSWER: To see if this part will fit your machine please enter the make, model, and year into our "Choose a vehicle" drop down boxes found above the product image. If your machine is not listed, we may not carry the right item for your application. If you have a 2017 year model but don't see your machine as an option, please contact a tech via Live Chat or call us at 1-800-336-5437 for assistance.
Is this a "c" piston?
Skip N on Apr 4, 2017
BEST ANSWER: What machine is this for?
Will this work on my Yz85?
A shopper on Dec 26, 2016
BEST ANSWER: To see if this part will fit your machine please enter the make, model, and year into our "Choose a vehicle" drop down boxes found above the product image. If your machine is not listed, we may not carry the right item for your application. If you have a 2017 year model but don't see your machine as an option, please contact a tech via Live Chat or call us at 1-800-336-5437 for assistance.
Does it come with gaskets?
A shopper on Dec 5, 2016
BEST ANSWER: No, gaskets are not included with this kit.
So what is the size of an "A" piston for a 2005 CR 250R ?
I have the stamp of "B" on the cylinder and the piston I ordered/rec is a standard 66.36mm, will this work or do I need to order a different size for "B"?
CHARLES S on Oct 19, 2016
BEST ANSWER: The diameter of the OEM A piston is 65.9mm. This kit should work with your cylinder as long as the ring end gap measurement is correct.
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