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Your cart is empty.Athena's Big Bore kit brings the raw power you have been missing in an easy to install, reliable package that bolts on with no machining needed in most cases, and includes easy-to-follow step-by-step installation instructions. Constructed from aluminum, the cylinder is lined with a nickel-carbide coating for durable, reliable performance, and the water jackets have been widened for a higher flow rate, cooling the cylinder, resulting in less power lost due to heat. Features a forged piston that's been molybdenum coated for high performance use and extended wear life. Includes: big bore cylinder, big bore piston, piston pin, piston pin rings, gasket kit. Note: To achieve optimum performance re-jet the carburetor with the available jet kits. Fits: Yamaha YZ 125 LC 1997-2004.
Customer
2025-08-26 14:57:52
Insane power, very impressed. Dropped to 47t sprocket and had to alter jetting. Fires first kick every time. Worth the money with supporting sprocket and carb work
Braden
2025-07-02 15:43:31
Missing cylinder head dowel pins. I cannot find them anywhere online and can’t rebuild bike now.
Customer
2025-06-20 13:24:16
My 02 yz125 had a good gain throughout the RPM range but was most noticeable at the bottom end. Unfortunately my brand new wiseco bottom end went out shortly after installing this kit and the piston met the cylinder head. Ordered a new piston and hot rods crank and installed a JD jetting kit. Bike runs better than ever now with the Athena 144 and JD jetting kit
Nathan S.
2025-06-08 20:58:26
Doesn't come with wrist pin bearing so if your bearing is bad this kit is not the one you want. 2 stars because for 600 bucks I think a 15 dollar bearing should be included. Can't find one on prime so no riding this weekend.
Leithkaub
2025-05-14 18:31:13
Awesome power but not worth 800$
Sean Phillips
2025-04-30 16:57:25
A+
Jdog
2025-04-11 15:50:22
This kit is a waste of money you will need to do a top end every 30 min. This is do to the fact that Athena has not made a groove for the middle gasket that keeps all you radiator fluid out. So what happens is that gasket will fail and it will hydro lock your bike. STAY AWAY.
jesse
2025-03-07 18:40:43
I just opened and im missing the insert that goes in the head... maybe called the combustion chamber? Ill leave another review after im done unpacking it all and seeing what is all supposed to be here..
jim l
2025-03-04 12:43:12
Great product. Beware the exhaust intake was changed from my 1997 YZ. Had to purchase a new one.
Kunde
2025-01-23 11:11:55
Die Qualität des Zylinders ist für das Geld unverschämt!Mir war bewusst dass, das Kurbelgehäuse bearbeitet werden muss, das genügend Platz für das Kolbenhemd ist.Die Verarbeitung der Kanäle ließ jedoch zu wünschen übrig! Es waren mehrere Spuren der Fertigung zu sehen. Kann nur Hoffen, dass sich keine Gusspartikel an den Überströmkanälen lösen und den Zylinder zerstören.Die Bohrung der Auslassschieberkanäle musste ich auch Aufwendig mit einer passenden Reibale bearbeiten damit dieses überhaupt in den Zylinder passen.Für 800€ deutlich tu teuer.
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