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TB YX90 Big Bore Kit 54mm - TBW9089


This kit is designed and manufactured by TB Parts who specialise in pit bike performance parts in USA. 


This is an aftermarket big bore kit to be used on the chinese 90cc (86cc) engines and TRX90 engines making it 114cc. 


The piston kit supplied is a high compression 54mm piston to help raise compression, if using with a stock cylinder head then the sparck plug spacer washer supplied must be used. 


The kit also contains a barrel with an alluminium casting opposed to the standard cast iron type reducing the engines weight and helping heat disapation. The cylinder is also coated for hard wearing piston wear. Cylinder casting height is 69mm.



  • This is a performance enhancing part and damage may occur when modifying an engine beyond standard specifications. Buyer to fit at their own risk.
  • If using with stock head then you MUST use the spark plug spacer washer supplied for the plug to piston clearence.
  • Will NOT fit Z110/125 Engines



  • YX90
  • TRX90

Item Includes:

  • 1x Piston 54mm (TBW0788)
  • 1x Piston Pin 13mm
  • 1x Piston Ring Set
  • 2x Piston Pin Clips
  • 1x Spark Plug Spacer Washer
  • 1x Gasket Set (TBW0318)
  • 1x Cylinder 54mm (TBW0721)

TB YX90 Big Bore Kit 54mm - TBW9089

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