Transform your Honda Grom or MSX125 with our Big Bore Kit Installation Service, expertly fitted by the leading Grom tuning specialists in the South East — MH MotorsportUK.

This package includes full professional installation of a complete Big Bore Kit, designed to deliver significant performance gains, enhanced torque, and a more responsive riding experience. The kit includes a high-performance camshaft essential for the LIGHT bore-up setup, plus an I-MAP fuel controller to ensure precise fuel injection and optimal engine performance.

For the best results and to maintain stability and reliability, we recommend replacing the muffler/exhaust system when fitting this kit.


This service includes:


  • Professional installation by MH MotorsportUK
  • Initial tuning and setup for maximum reliability and performance
  • Expert advice and aftercare support
  • Aluminum cast iron sleeve cylinder
  • Displacement: 181cc

  Bore diameter: φ63

  Stroke: 57.9mm

  • Piston: Casting (3R) specifications
  • Compression ratio: 11.1:1 (normal: 9.3:1)
  • I-MAP injection controller included
  • O2 sensor Feedback canceller included
  • Unleaded premium gasoline specification
  • full size oil cooler with custom in-house low mounting bracket
  • 1.3l of 10w50 oil (increased capacity with new oil cooler)



Important Information:

  • This listing includes installation — you’ll need to arrange to drop off your bike at our workshop.
  • Collection and delivery services are available for an additional fee. Please contact us to arrange this.
  • MH MotorsportUK are the leading specialists in Honda Grom / MSX performance tuning and upgrades across the South East.


Unlock the true potential of your Grom with MH MotorsportUK — precision performance, expertly installed.



*Because it exceeds 125cc, it cannot be used on general public roads.

Honda Grom/MSX 181cc BigBore 2013-2015 Full supply and installation

£780.00

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