426 Big Bore Kit
+3mm (88mm) big bore kit, includes JE Pistons complete piston kit and a
Cometic top-end gasket kit. This kit for your 400EX, 400X or XR400 gives a noticeable power increase without a loss in reliability. Available in 2 different compression ratios.
This kit requires your stock cylinder to be bored and honed – if you’d like us to do that work, just contact us.
Honda TRX400EX 1999-2008
Honda TRX400X 2009-2014
Honda XR400 1996-2007