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Vertex 2-Stroke Piston Kit - Stock Bore

$101.93 - $247.93
$84.98 - $194.98
4.50 5 40
4.50 out of 5 stars

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Vertex 2-Stroke Piston Kit - Stock Bore
Vertex 2-Stroke Piston Kit - Stock Bore
  • Description
  • Reviews (40)
  • Q&A (29)
  • Fitment

The MotoSport.com Vertex 2-Stroke Piston Kit - Stock Bore includes one of each of the following components with the following attributes:

Vertex 2-Stroke Piston Kit:

Important Note: This piston is for a stock sized bore. Please measure your cylinder to check clearance before ordering.

As the O.E. supplier of two-stroke pistons to KTM, Vertex Pistons has an outstanding reputation for quality and performance. Each gravity cast piston is created with only premium aluminum alloys utilizing an 12 - 21% silicon content.

The silicon content in Vertex pistons is crucial to the quality of the piston. Silicon is critical in decreasing thermal expansion which, when an engine reaches normal operating temperatures, can change the geometry of the piston. Controlling this expansion means that a Vertex piston can be run at tighter tolerances for more power, less noise and a longer lifespan of the piston. Plus, the silicon content decreases wear on the piston skirt which also aids in the life of the piston.

In addition to the silicon, each Vertex piston utilizes a unique Molybdenum Disulphide (MOS2) coating which aids in the break-in process and reduces overall wear.

Vertex Piston includes:

  • Premium quality Vertex piston.
  • Complete set of nitride coated or chrome-plated piston rings.
  • Fully case-hardened wrist pin.
  • Circlips.
  • Competitive price!

Hot Rods Needle Bearing:

  • Case-hardened and silver coated, the bearings are just as tough and reliable as all Hot Rods parts.
  • Wrist pin bearing is specially designed with a long shouldered bearing cage to withstand high RPM use.
  • Can be used with Hot Rods connecting rods and O.E. or aftermarket pistons.

Cometic Top End Gasket Kit:

State-of-the-art gaskets is what Cometic has been doing since its inception in 1989. This comes from their dedication to constructing gaskets for the most demanding race circuits like AMA and NASCAR. Today's lightweight engines are producing more horsepower, higher cylinder pressure, clamp load and extreme temperatures. Cometic's commitment is to provide innovative, quality gaskets while maximizing your engine's power and performance.

Cometic meets the needs of each specific gasket by using materials to match. Even the basic top end gasket kit features different materials for each gasket. The head gasket is constructed from non-asbestos, flexible graphite that is laminated to a stainless steel core. The manifold and base gaskets are constructed from non-asbestos nitride rubber-bound fiber. Cometic also includes copper gaskets where needed.

Cometic designs and builds their gaskets in the U.S.A.

Note: Image is for reference only, actual Kit may vary based on contents and fitment.

4.5 out of 5 stars (40)
4.5 out of 5 stars
5 star   35
4 star   7
3 star 0
2 star   1
1 star   3
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1-10 of 40
Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Verified Purchaser
Location: San Diego, CA, USA
Loaner
Easy Top End Package

This gave me everything i needed to swap out the top end on my KTM. What a dream, no running back to the shop for a gasket, or needle bearing. I highly recommend this kit, and the Vertex pistons have lasted for me with no issues.

Overall 4 out of 5 stars
Ease of Installation
Performance
Power
Style
Verified Purchaser
Location: Abbeville, SC 29620, USA
pmdparts
Nice product--but beware of "A" ,"B", or "C"sizes

Ordered this kit for 2013 KTM 85 sx. Description says "standard bore'" but apparently, KTM produces engines with "A", "B", and "C" bores from the factory. These are just three different size pistons that vary by a fraction of a millimeter and are fit to each motor individually to help account for variance in machining and plating of the bores. The piston I received was a "B" unit and it turns out that our bike was fitted with a "C" piston from the factory. I wish that the item description had spelled this out so that I could have gotten the "c" piston instead, but there was no mention of this in Motosport's description. I installed the "b" unit and I'm sure it will be fine since I will replace it in about 20 hours anyway.

Overall 1 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Verified Purchaser
Location: Modesto, CA, USA
Rider13
Faulty product

Shortly after installation of this piston and break in my engine seized. A large chunk of the top of the piston broke off wedging itself between the head and the remaining piston, destroying not only my new piston, but also my cylinder and head.

Overall 4 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Verified Purchaser
Location: DTown Racer
DirtLife
First Top end rebuild on 85r Honda

Researched rebuild days before part showed up. Made job easy.

Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Verified Purchaser
Location: Texas, USA
1Racing

Great replacement for stock.

Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Verified Purchaser
Location: Atlant Ga
Pickle
Great top end

Never have a problem with this top end in my sons yz-85

Overall 4 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Verified Purchaser
Location: Montana, USA
speedy
Good kit

everything you need

Overall 4 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Location: Western PA
DirtWarrior
2 Stroke Power!

This is a great rebuild kit. Very high quality parts. The only improvement that I think could be made is if Cometic decided to put a paper in their gasket kit that labeled each individual gasket and O-ring. Other than that, fantastic product. Just as good, if not better than Wiseco.

Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Verified Purchaser
Location: Edmond, OK
brokendad
Top End Kit

Restore the power in your bike byu using quality parts!

Overall 5 out of 5 stars
Durability
Ease of Installation
Performance
Power
Style
Verified Purchaser
shnedy
Great product vertex piston

Got the piston kit for my cr 125 it had no compression.
After i replaced the piston and ring wow what a difference. Before i changed it i was able to start the bike with my hand. Those days are over .
Great product.

1-10 of 40
Total Questions (29)
Questions with answers:
  27
Questions without answers:
  2
raese Location: Germany
Piston size.
Moe987 Location: Reno
1-10 of 29
Deland 5 days 12 hours ago Location: Orangeburg, SC, USA
May I use this piston kit with the Athena cylinder?
raese 5 days 15 hours ago Location: Germany
Is this piston 54.00 mm big or what because i have an 2007 yz 125?
Dylan22 3 months 25 days ago Location: Georgia, USA
Will a size c fit a 2004 KTM 125sx that has had a stock piston in it?
I have a 2004 KTM 125sx and I would like to know if there Is a real big difference in piston sizes for this bike. The piston hasn't been changed before I don't think.
MotoSport Staff Expert
3 months 24 days ago
MotoSportExpert
Vertex offers A, B, C, D, sizes so that the customer can properly fit each piston to the cylinder. The difference in the sizes is 0.01mm (0.0004") increments with A being the smallest and D the biggest. When a cylinder wears, the customer can choose the next larger piston size to regain the proper factory fitment. If you are just replacing the piston, then you need to first know the bore of the cylinder. This can be done by using a bore gauge to find the diameter or by reading the owner’s manual to find the bore specifications. Ultimately, the bore should be measured for the best possible results. After the diameter is known, then you can pick which size piston will work best in your cylinder. Remember to maintain about a 0.05mm (0.002”) piston to cylinder clearance, depending on application. If you are having a cylinder re-plated, then you will want to choose a piston of the OE bore size (an A or B size is probably best). When you send the piston and cylinder away to get re-plated, the plating facility will match the cylinder bore to piston diameter. If you have a cast iron bore cylinder and you are sending the piston and cylinder off to a machinist to be bored out, then you will want a piston that is oversized from the current diameter. For example: If your current bore is 64.00mm, then you will want to choose a 64.50mm or similar oversized piston. The machinist boring the cylinder will bore and hone the cylinder to match the piston size.
Also, feel free to give us a call at 888-676-8853 and we would be happy to help you out with your order.
Moe987 4 months 18 days ago Location: Reno
Piston size.?
I just returned a kit that came with a piston that was 66.40. Will this fit mine which needs a max of 66.35?
Expert MotoSport Staff
4 months 17 days ago
MotoSportExpert
The stock bore Vertex 2-Stroke Piston Kit (22584B) for your 2004 Yamaha YZ250 would be 66.35mm. Also, feel free to give us a call at 888-676-8853 and we would be happy to help you out with your order.
cartwright 4 months 29 days ago
What size bore is a 99 yz125?
Im trying to bore over my 99 yz 125 but I don't know if I need a big bore kit or can I just get a bigger piston and resize my own cylinder. I need to know what size is my stock cylinder.
MotoSport Staff Expert
4 months 28 days ago
MotoSportExpert
Stock bore on the 1999 Yamaha YZ125 would be 54.00mm. Feel free to give us a call at 888-676-8853 and we would be happy to help you out with your order.
edd653 Over 5 months ago Location: London, UK
Oversized pistons?
Are you able to get 0.5/1.0mm oversized pistons for yz 125 (05)
Expert MotoSport Staff
Over 5 months ago
MotoSportExpert
If the part is available through one of our suppliers, we would be happy to order it for you. Please contact one of our sales professionals to inquire about special orders and availability.
Dirt Bike / ATV: 1-888-676-8853
Kawasaki Over 6 months ago
What is the stock size for a 2004 kx 125?
I ordered a vertex piston and just rid the cylinder and got it re-sized and the piston wiggles side to side is that ok?
MotoSport Staff Expert
Over 6 months ago
MotoSportExpert
This stock bore Vertex Piston would be 53.96mm. You need to first know the bore of the cylinder. This can be done by using a bore gauge to find the diameter or by asking the machine shop who did the work. If you had the cylinder bored and replated you would need to go to the next size up.
Remember you want to maintain about a 0.05mm (0.002”) piston to cylinder clearance.
Javon Over 6 months ago Location: Jamaica
Can this fit my 03 Yamaha yz 125 2 stroke ? My piston only has 1 ring?
Expert MotoSport Staff
Over 6 months ago
MotoSportExpert
Yes this Vertex 2-Stroke Piston Kit will fit your 2003 Yamaha YZ125. Just be sure to correctly select the Year/Make/Model of your bike before ordering so we can be sure to send you the correct kit for your bike. Also, feel free to give us a call at 888-676-8853 and we would be happy to help you out with your order.
*The image is a generic image supplied by the manufacturer for reference only. It may not be displaying the exact part for your bike.
wireman Over 7 months ago Location: Kentucky, USA
I have a cr 125 02 does it come with two rings?
Expert MotoSport Staff
Over 7 months ago
MotoSportExpert
For your 2002 Honda CR125 it would be a single ring.
sebasdono Over 7 months ago
This kit fit exactly in a KTM 250 EXC 2012 made in AU???
MotoSport Staff Expert
Over 7 months ago
MotoSportExpert
All products sold on Motosport.com are for US models only. We unfortunately do not have product fitment for non-us models.
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