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Wiseco Piston Kit

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Wiseco Piston Kit
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Wiseco Piston Kit Pro-Lite Standard (66.4 mm)

Fits: 2004 KAWASAKI KX250
Part# 1038400189 | Mfg Part# 799M06640

Our Price: $112.05

MSRP: $154.00 - You save $41.95 (27% off)

Get $2.24 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

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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How To - Rebuild A Top End

Details

  • Lightweight forging for instant throttle response and maximum torque .
  • Computer engineered piston skirt profiles provide minimal cylinder wall friction .
  • Piston kit includes piston, rings, wristpin and circlips.
WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

Wiseco Piston Kit Reviews

Each review submitted enters you into a
$100 gift card monthly drawing and a
$500 gift card quarterly drawing!
 
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4.8 / 5.0
491 Reviews
5 Stars
4 Stars
3 Stars
2 Stars
1 Star
430
49
6
4
2
Value
4.8 / 5
Durability
4.8 / 5
Fitment
4.9 / 5
Performance
4.9 / 5
Recommend it?
Yes (200)
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
YZ 65 kit
Noticeable difference in power and sound. The head gasket went on the bike and it lost compression, but I went ahead and did this while it was apart. Glad I did. Running better than new. Thanks

-m-2018 YAMAHA YZ65--
November 21, 2019
Mogadore, OH, US
Age: 45-64
Purchased
 4 days ago
Gender:
Male
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Wiseco piston kit
Fit like it should and performs like new. Pay attention to arrow etched on top of piston (direction of air travel, or you take a chance of impacting a valve) for correct installation as instructions did not specify!
October 2, 2019
Phoenix, AZ, US
Purchased
 2 months ago
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Great fit!
Perfect fit and delivery. Happy I chose this product.

-m-1998 KTM 300 EXC--
September 25, 2019
Blairstown, NJ, US
Age: 45-64
Purchased
 1 year ago
Gender:
Male
Weight:
221 - 250 lbs.
Height:
>6'7
Value
4 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Wiseco all the way.
Wiseco makes great pistons. Great quality, durability, and they just look awesome! These things will last a long time.
September 25, 2019
Prescott, WI, US
Age: 15-24
Purchased
 2 months ago
Gender:
Male
Weight:
131 - 160 lbs.
Height:
5'10 - 6'0
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Very high quality
Very high quality piston and ring set and worked very good highly recommend to anybody

-m-2009 YAMAHA TTR125E--
September 17, 2019
Cardigan, PE, CA
Age: 15-24
Purchased
 3 months ago
Gender:
Male
Weight:
191 - 220 lbs.
Height:
5'7 - 5'9
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
This piston was very powerful and add almost 30 more horsepower to my kfx400.

-m-2006 KAWASAKI KFX 400--
August 28, 2019
Tallahassee , FL, US
Age: 15-24
Purchased
 3 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
Piston
Great Products.......always fast shipping........great prices
August 4, 2019
29340, SC, US
Age: 25-44
Purchased
 1 year ago
Gender:
Male
Weight:
191 - 220 lbs.
Height:
5'7 - 5'9
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Best aftermarket top end I have used.
Been using Wiseco top ends for many years with no issues and great performance. Will continue to use them for future builds, maintenance.

-m-1996 HONDA CR250R--
July 22, 2019
Denton, TX, US
Age: 25-44
Purchased
 1 year ago
Gender:
Male
Weight:
191 - 220 lbs.
Height:
5'10 - 6'0
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Wiseco
Cant go wrong with wiseco did have an issue this time but rma took careof it quickly
July 12, 2019
Philadelphia, NY, US
Age: 25-44
Purchased
 4 months ago
Gender:
Male
Weight:
221 - 250 lbs.
Height:
6'1 - 6'3
Value
5 / 5
Durability
5 / 5
Fitment
5 / 5
Performance
5 / 5
Recommend it?
Yes
Great durability
Love wiseco piston kits. They have plenty of power, and last between 150 and 200 hours if properly jetted.
May 29, 2019
PROVO, UT, US
Age: 25-44
Purchased
 over 3 years ago
Gender:
Male
Weight:
191 - 220 lbs.
Height:
6'1 - 6'3
Each question or answer submitted enters you into a:
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$500 gift card quarterly drawing!
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Start typing your question and we'll check if it was already asked and answered. Learn More
Browse 65 questions Browse 65 questions and 142 answers
Does this kit include all the gaskets needed as well as the piston?
Brandon P on Mar 26, 2017
BEST ANSWER: Just piston, rings and circlips. You will need to buy a separate gasket kit. I would recommend ordering and replacing the wrist pin also while it's tore down.
Does this kit also come with the piston pin bearing?
A shopper on Dec 4, 2017
BEST ANSWER: No, it doesn't. The Pro-X bearing is Japanese made, good price. I always use them.
why doesn't the top of this piston have the 4 circles?
Rudy P on Sep 13, 2017
BEST ANSWER: Rudy,
It is just Weisco's design. Other manufacturers try different things to make their product different or better. It's a great piston. Weisco teflon Coates their pistons for extra protection. I have never had one not make it to the next overhaul.
So it doesn’t come with a wristpin? It says its included in the details
Tyler B on Jun 19, 2018
BEST ANSWER: Yes..Wiseco piston kits include wrist pin, wrist pin clips and ring set.
Can this be used in an AMA stock class race?
A shopper on May 7, 2018
BEST ANSWER: Yes as long as you don’t change the displacement or stroke of engine you are in compliance.
Does this kit come with all the gaskets for the rebuild?
A shopper on Mar 29, 2019
BEST ANSWER: No gaskets at all. You’ll even need to buy the top end bearing with this or any piston kit.
Wiseco Pro Lite piston kits have been the most durable for me and vibrate MUCH less late in the season.
From my experience, the Cometic steel/fiber complete gasket kits are the best by far. The steel layer prevents tearing if you ever need to remove a cover or head. They’ve cost just a little more and you’re life will be easier ...really.

Hope this helps.

Best,
John
My Piston only has one clip , and this one has two clips, is there any difference between one clip and two clips?
Sebastian C on Apr 4, 2018
BEST ANSWER: Your piston should have a clip on both sides just like the piston you will receive. There is a little groove on each side of the piston and you have to remove one clip to get the wrist pin off of the rod. I always put one in the piston before I put the piston back on the rod so I only have to put one clip back in once the piston
is in the machine.
My compression ratio is 12:0:1. This piston is 12:4:1 is this a higher compression piston?
AARON H on Nov 13, 2018
BEST ANSWER: Yes, it is slightly higher but, not outrageously higher. You will need to use higher octane fuel but it will give you better performance overall. If you are already using the highest octane fuel you can buy you should be OK with no change. Your bike should run great. Higher compression in a two stroke is generally a good thing.
just to make sure I'm getting the right piston for my cylinder , when the description states "standard " (xx.xmm) does that mean the piston is that size or thats the piston for that bore? i caliperd my bore and its 66.4mm
Michael G on Jan 19, 2018
BEST ANSWER: It means it is for that bore or it is a standard size cylinder hasn’t been touched it is stock
If you have re sleeved the cylinder with a steel sleeve will the rings work?
SAMUEL M on Dec 24, 2017
BEST ANSWER: I apologize, I don’t have an answer to that. I assume so as long as the bore is correct.
For chrome plated cylinder?
A shopper on May 24, 2019
BEST ANSWER: yes for all cylinders all my dirt bikes have chrome plated cylinders and i use this piston.
Is the actually bore of this piston 54mm or is it 53.xx?
Tyler B on Jun 21, 2018
BEST ANSWER: Check wiseco website for available sizes.They make a standard size and sometimes up to 3 or 4 oversized pistons.Measure bore in 4 places with Inside micrometer or telesopic gauges first and then check for available sizes.
ordering it for my 16 rmz 250 is this the high compression piston ?
chris t on Jun 2, 2018
BEST ANSWER: The one I ordered was the wiseco but it was for my son's cr85 which was the high compression..if this is the same but different size I would assume it is high compression.
How often should i replace a piston?
A shopper on Apr 5, 2018
BEST ANSWER: it really depends on how the bike is being used; small bore with a fast kid racing 8hrs +/-, 250 race mode 25hrs,250 old slow guy 50-100hrs.
If the piston in my cr125 was 53.94mm and i'm putting in a wiseco 54mm, will it still work in the cylinder?
James L on Feb 26, 2018
BEST ANSWER: Where did you're measurement come from?53.94m.and yes it would b .06 mm different which is super close run it
89 YZ 250 - Bought new Wiseco piston - Prolite .020 (68.5MM), for 1989 YZ250WR. Bike has original bore (68mm - cast iron sleeve) - no score marks. Ring end gap was excessive on old rings, but no blow by on stock piston. Had 170 compression. Bike was getting hard to start. Was told to bore to next size up so that is why bought this piston. Took to machine shop today with new piston. Also brought cylinder head with me and they said that they do not need the cylinder head? I thought that the inside radius of the cylinder head needed to be opened up to accommodate the new piston/bore size? Also asked if they would champher/round edges on all ports inside cylinder after bore? They said no need to? Also wondering if power valve will need to be shaved? Anyone have any answers? Any suggestions?
Brian W on Jan 2, 2018
BEST ANSWER: Your machine shop is correct, the piston does not protrud the top of the cylinder. Also correct on rounding the edges, no need to. As far as the power valve goes I would check on reassembly.
will this fit a 2001 cr80? stock bore
james b on Sep 14, 2017
BEST ANSWER: Yes, the standard 47mm pro-lite piston is meant as a stock bore replacement with unmatched reliability from wiseco's race proven pistons
I have a 89 yz 80 the cylinder is 49mm what size piston will fit. The 48.5mm or no?
Chris T on Sep 5, 2017
BEST ANSWER: As long as its a standard bore and hasnt been altered by replating or sleeving the piston that wiseco reccomends will be the correct size.
I have a 2016 yz250 x

I want to rebuild top end over the winter. I want to go bigger.

Where do I see a chart of sizes which are available so I can see how big I can go?
A shopper on Sep 5, 2017
BEST ANSWER: On a 2016 the only way to go bigger is to buy the big bore kit. You can't bore the factory cylinder without putting a sleeve in it which would cost the same as the big bore kit with a new cylinder
it's for 2 times?
A shopper on Jun 20, 2017
BEST ANSWER: That's a vague question at best. But it is the second oversize bore from the stock piston if that's what u mean
Does this piston come coated or plain? Does it come with a TiN coated ring or plain ring?
Alexander H on Jun 15, 2017
BEST ANSWER: Mine was plain got it for my 2001 kx 125.
For a 2007 Yamaha yz 125 there are 4 different piston sizes to choose from. This piston only has one size when I enter my bike. Will it work or should I order OE?
Charles B on Jun 10, 2017
BEST ANSWER: You should alway check the piston size that came out of you machine to insure proper fit although most bikes have the metric size it is easy to figure out if it is a 65mm piston and you want it .020 over then it is 65.5 or to make it 66mm then it’s .040 over std size
Will this fit my 04 trx450 bored to a 96mm.?
armando s on Apr 4, 2017
BEST ANSWER: Select the correct size of piston upon checkout. Be aware must hone cylinder before installation of this piston.
Will this work good for 08 kfx450r rebuild? Any boring needed to be done?
Michael F on Mar 14, 2017
BEST ANSWER: As long as the cylinder is standard bore and the plating is good, this piston will work great in your bike. Always do a light hone to the cylinder whenever doing a piston replacement. It helps the rings seat and wear correctly. These pistons are one of the best on the market. I hope this helps.
I have a 2006 trx450r what is the compression rating for this piston on my atv?
Tyler A on Mar 4, 2017
BEST ANSWER: As long as it's not the high compression piston, it's the same as stock which I believe is 11:1
Is the standard Raptor 250R piston stock compression or the higher 10:5-1?
Jeff P on Oct 20, 2016
BEST ANSWER: If it's standard then it's stock compression
What octane do I need for 12.9:1 compression on a 2006 crf250r?
Owen G on Jun 6, 2019
BEST ANSWER: You can run any pump gas from 87-92 or if you got the many you can run 100-110
I have a 2007 CR 250, is this piston coated? Also, is this piston a double or single ring?
DOUG B on Oct 5, 2018
BEST ANSWER: double ring and the skirt should be coated. The racers choice wiseco is a single ring and coated as well
Does this piston come with exhaust bridge holes pre-drilled? 2005 YZ250
Dalton M on Sep 13, 2018
BEST ANSWER: No the holes are not pre-drilled, but they do give detailed instructions on how/and where to drill them
The piston that says it fits my '05 CRF450x says it is 96mm. Should I be concerned that the service manual says that my piston should be between 95.97mm-95.98mm?
Erik A on Jul 7, 2018
BEST ANSWER: it should be fine
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