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Athena Big Bore Complete Cylinder Kit

(6 reviews)

Item: 327770

$175.03 – $1348.16

Select Your Vehicle - Fitment Guaranteed

Athena Big Bore Complete Cylinder Kit


  • Includes aluminum cylinder with nickel-carbide coating on 2-stroke machines and galvanic coating on 4-stroke machines
  • Specially designed, high performance, forged piston kit
  • Included top end gasket set comes with all required seals and hardware
  • Easy to follow, step by step installation instructions
  • Made in Italy
Specification Details
Bore Varies (make selection above)
Compression Ratio Varies (make selection above)
Country of Origin Italy
Displacement Varies (make selection above)
Material Varies (make selection above)
Size Over Standard Varies (make selection above)

Vehicle Fitment


Fitment is guaranteed or your money back plus free return shipping.
Don’t waste time installing a product that doesn't fit. We worked hard ensuring that this product is an exact fit on the vehicles listed below.

Arctic Cat
  • DVX 400 2004-2008
Honda
  • CRF150R 2007-2009
  • CRF150R Expert 2007-2009
  • CRF230F 2007-2009, 2012-2015
  • CRF250R 4-Stroke 2004-2009, 2018-2023
  • CRF250X 4-Stroke 2004-2009, 2012-2013
  • TRX450ER Sportrax 450ER 2006-2014
  • TRX450R Sportrax 450R 2006-2014
Husqvarna
  • FC 250 2016-2022
  • FE 250 2017-2019
KTM
  • 250 EXC-F 2017-2019
  • 250 SX-F 2016-2022
  • 250 XC-F 2016-2022
  • 65 SX 2001-2008
  • 65 XC 2008
Kawasaki
  • KFX400 2003-2006
  • KLX400R 2003-2004
  • KLX400SR 2003-2004
  • KX125 2003-2005
  • KX250 4-Stroke 2019
  • KX250F 4-Stroke 2009-2012, 2017-2018
  • KX450F 2009-2015
  • KX65 2002-2023
Suzuki
  • DR-Z400 2000-2004
  • DR-Z400E 2000-2007
  • DR-Z400S 2000-2017, 2019
  • DR-Z400SM 2005-2009, 2012-2017, 2019
  • LT-R450 QuadRacer 450 2006-2011
  • LT-Z400 QuadSport 400 2003-2014
  • RM-Z450 2005-2006, 2008-2017
Yamaha
  • CW50 Zuma II 1997-2001
  • WR250F 2001-2012
  • WR250R 2008-2013
  • WR250X 2008-2011
  • YFZ350 Banshee 1987-2006
  • YFZ450 ATV 2004-2009
  • YJ50R Vino 50 2001-2004
  • YJ50RA Vino 50 Classic 2002-2005
  • YW50 Zuma 50 2002-2005
  • YZ125 1997-2021
  • YZ250 2-Stroke 2003-2023
  • YZ250F 4-Stroke 2001-2007
  • YZ450F 2018-2019
  • YZ450FX 2018-2019
  • YZ85 2002-2024

Customer Reviews

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Awesome

By   on  Verified Purchaser

Awesome kit. Son has put 100 hours on this kit so far with no issues.


Big bore

By   on  Verified Purchaser

I had no problem with this kit...big bore kit works good....got mine all broke in and it runs really good...glad I got it...


Runs great

By   on  Verified Purchaser

Bolts right on. No grinding on crankcase necessary for 1999 yz125. Runs great


Everything’s good but the power valves

By   on  Verified Purchaser

Everything was good until I tried putting the power valves in. The valves didn’t fit correctly so I had to file them down to make them seat all the way in correctly. Other than that it all seems good.


Double thumbs up

By   on  Verified Purchaser

Bought the big bore kit for a 2006 klx110, very high quality kit comes with everything you need. The kit is the best bang for your buck. Really wakes the bike up.


Very good

By   on  Verified Purchaser

Made my ltz400 a missile.


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Questions & Answers

Ask Question

would this bolt up to my 97 yz125?

Yes, this kit is offered for that 1997 YZ125. However, you would need to use a pipe from a 1999-2004 YZ125 due to the way the cylinder in this kit is made. It will only work with a pipe from that 1999-2004 YZ125. Other than that, you would just need to machine the cases as shown in the included installation instructions to provide enough clearance for the big bore piston.

By Andy
Answer Question

Stock Yamaha Banshee, can i throw these on a stock banshee without having my case milled?

Is this bolt on and rip? Can i throw these on a stock banshee without having my case milled?

Yes, the kit can be installed on the Banshee engine without any machine work being done.

By Andy
Answer Question

Will it fit to 2007 kawasaki kx65

Yes, there is a 80cc kit offered for that 2007 KX65.

By Andy
Answer Question

2000 yz125, does machining need to be done on this model?

Yes, the kit for that 2000 YZ125 would require you to machine the cases in order to provide enough clearance for the piston.

By Andy
Answer Question

what will i need and will i have to modify the crankcase on a 1999 yz 125

You will need to have the cases machined in order to allow the clearance needed for the larger piston.

By Andy
Answer Question

Will I need to mod the case on my 01' yz 125?

Yes, you would need machine the cases in order to allow the clearance needed for installation of this kit on the 2001 YZ125. The included installation instructions clearly show how much and where to took out the material.

By Andy
Answer Question

do I need to do anything to bottom half for a banshee

There is not case machining that needs to be done in order to install this kit on the Banshee.

By Andy
Answer Question

Will this bolt right on 2006 kfx400 or will I need case work

Yes, this would be a bolt on kit for that 2006 KFX400. No case machining required.

By Andy
Answer Question

Will this be a direct bolt on for a yz85 or does it require case work?? Also does the crank work with stock bearing or do I need specific crank bearings?

Also does the crank work with stock bearing or do I need specific crank bearings?

Yes, you would need to machine the cases to allow proper clearance. Yes, the crank included would work with the stock style bearings.

By Andy
Answer Question

I own a 2003 kx125 is there any grinding or modification to the crankcase before installation ?

Yes, the kit for the 2003 KX125 would include having to open up the cases in order to allow fitment of the new components.

By Andy
Answer Question

Will it fit a 2001 yz125

How much would it cost

As long as that is the bike that you choose before adding the kit to your cart, it would be a fit.

By Andy
Answer Question

Will this work for my 1999 YZ 125

So long as you choose that 1999 Yamaha YZ125 when adding to your cart and you have a stock stroke length crank installed, you should have no fitment issues.

By Andy
Answer Question

Hi guys I'm just curious to know if this is a straight bolt on kit or am I gonna have to modify anything on my 1997 YZ 125

Hi guys I'm just curious to know if this is a straight bolt on kit or am I gonna have to modify anything on my 1997 YZ 125 and do the power valves include Springs rod and everything else needed for the cylinder

According to Athena, to assemble this cylinder kit on models YZ 125 1997-1998, you have to replace the original pipe with a version for the year 1999-2003 and for 1997-1999 models you have to order the 2-torsion original springs (valve) Yamaha year 2000-2003.

By Andy
Answer Question

Can I run this on my 2018 crf 450r

Yes, there is a kit offered for that 2018 Honda CRF450R. Just be sure you choose that model before adding it to your cart.

By Andy
Answer Question

I've got a 04 yz250 can I use my same power valve or do I need to order a new one

The kit for that 2004 YZ250 would actually include a new power valve.

By Andy
Answer Question

would i have to run race gas with the compression ratio being 13.8.1

You should be good with running premium grade fuel, 93 octane or higher.

By Andy
Answer Question

i have a 2019 fc 250 looking to get the 276 kit can i use stock cams or hot rod performance cams

You would be able to use stock cams or aftermarket cams with this kit.

By Andy
Answer Question

I have a 2005 Ltz 400 . Purchasing this big bore but my question is do I have to upgrade my carb or just get bigger jets ? Thank you

Yes, it would be recommended to use larger jets with the install of this big bore kit.

By Andy
Answer Question

Will I need to grind the case for clearance of the piston skirt?1998 yz 125

1998 yz 125

For the 1998 YZ125, it would not be necessary to modify the cases to install this kit.

By Andy
Answer Question

can I get a big bore kit for my 2003 crf230f that would make it a 250?

I only see that we offer a 240cc kit for that bike. If you search our site for BBR 240cc Big Bore Kit, you should have no problem finding it.

By Andy
Answer Question

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