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Yamaha YZ250 Big Bore Kits




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*Please be sure to clean out your crankcases before installing your big bore top end. There may be foreign material still inside from a prior top end failure, which will quickly ruin your new big bore kit. Also check your crankshaft to make sure your lower end bearing is not ready to fail. If you need us to check it for you, then send your entire engine to us when purchasing our big bore kit service.

 265cc Big Bore Kit Service  Send us your cylinder, power valve, and head. Includes: Bore Cylinder and Re-Plate, Head Modification for 68.5mm bore, Big Bore Porting, any Power Valve Modification needed, 68.5mm Forged Piston Kit, Top End Gasket Kit, and Return Shipping.
Price $630.00   For 1999-11 YZ250
 

275cc Big Bore Kit Service  Send us your cylinder, power valve, and head. Includes: Bore Cylinder and Re-Plate, Head Modification for 69.5mm bore, Big Bore Porting, any Power Valve Modification needed, 69.5mm Forged Piston Kit, Top End Gasket Kit, and Return Shipping.
Price $630.00   For 1999-11 YZ250
 

295cc Big Bore Kit Service  Send us your cylinder, power valve, and head. Includes: Bore Cylinder and Re-Plate, Head Modification for 72mm bore, Big Bore Porting, any Power Valve Modification needed, 72mm Forged Piston Kit, Custom Top End Gasket Kit, and Return Shipping.
Price $630.00   For 1999-11 YZ250
 

305cc Big Bore Kit Service  Send us your cylinder, power valve, and head. Includes: Bore Cylinder and Re-Plate, Head Modification for 73.5mm bore, Big Bore Porting, any Power Valve Modification needed, 73.5mm Forged Piston Kit, Custom Top End Gasket Kit, and Return Shipping.
Price $630.00   For 1999-11 YZ250
  

 265cc Big Bore Parts Kit Only  Includes: Wiseco 68.5mm Piston Kit  #804M06850, Cometic Top End Gasket Kit, and Top End Bearing.
Price $199.00   For 1999-01 YZ250
 

 265cc Big Bore Parts Kit Only Includes: Wiseco 68.5mm Piston Kit  #804M06850, Cometic Top End Gasket Kit, and Top End Bearing.
Price $199.00   For 2002-11 YZ250
 

275cc Big Bore Parts Kit Only  Includes: Wiseco 69.5mm Piston Kit  #526M06950, Cometic Top End Gasket Kit, and Top End Bearing.
Price $227.00   For 1999-01 YZ250
 

275cc Big Bore Parts Kit Only  Includes: Wiseco 69.5mm Piston Kit  #526M06950, Cometic Top End Gasket Kit, and Top End Bearing.
Price $227.00   For 2002-11 YZ250
 

275cc Big Bore Parts Kit Only  Includes: Wossner 69.5mm Piston Kit  #8156D350, Cometic Top End Gasket Kit, and Top End Bearing.
Price $187.00   For 1999-01 YZ250
 

275cc Big Bore Parts Kit Only  Includes: Wossner 69.5mm Piston Kit  #8156D350, Cometic Top End Gasket Kit, and Top End Bearing.
Price $187.00   For 2002-11 YZ250
 

295cc Big Bore Parts Kit Only  Includes: Wossner 72mm Piston Kit  #W845PS, Custom Top End Gasket Kit, and Top End Bearing.
Price $217.00   For 1999-11 YZ250 

305cc Big Bore Parts Kit Only  Includes: Wossner 73.5mm Piston Kit  #W845P6, Custom Top End Gasket Kit, and Top End Bearing.
Price $217.00   For 1999-11 YZ250