Yamaha Big Bore Service
Our prices below includes cylinder sleeve installed, Top End kit and all necessary modifications ( bore, port, powervalve machined, head re-chamfer to work with larger piston)

If you need to increase displacement then increasing the bore size is the best option. You cannot go wrong with an ACAS works Big Bore kit. ours is quite reliable and the most reasonable on the market today.. 

The process is a simple as follows. 

  • Remove your jug

  • Remove the studs and all other items not needed for the Mod ( we charge extra for this removal)
  • leave the powervalve in,
  • Send the cylinder head
  • Fill out the Job Order form completely and put it in the box
  • If you do not see your cylinder model in the drop down, then write it in the notes
  • Pack your jug properly to avoid damage during shipping
2 Stroke Yamaha Big Bore ( this will include a wiseco, Namura or Prox Top End kit)
YZ80  90cc      bore  49mm          1993 -04        $300
YZ80  103.5cc   bore  52.5mm        1993-04         $360
YZ85  92cc       bore 49.5 mm       2000-14         $300
YZ85  103.5cc   bore  52.5mm        2000-14         $360
YZ125 134cc      bore  56mm          1999-17         $400