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DHM High Compression Stock Bore Piston for the 2022+ Honda Grom / Monkey (Gen 2)

$120.00
by DH Motoring
Include NGK CR9E Spark Plug

 

 **Professional install is highly recommended. Ring gaps must be set, and base gaskets must be installed properly. Setup sheet is included and can be viewed HERE.

DH Motoring Stock Bore Racing Piston (2022+ Grom / Monkey)

We've now produced the first high compression stock bore piston for the new 2022 Grom/Monkey. We took our development experience from the previous generation Grom and CRF110 and applied it to the all new Grom engine and have come up with a lightweight, high compression piston that still utilizes the OEM 12mm pin size. 

  • ~12.4:1 compression 50mm stock bore piston
  • 100% Forged construction
  • Larger ring and skirt oiling holes than other pistons on the market
  • Larger oil spring to increase oil volume between the oiling rings
  • OEM sized skirt area to maintain reliability
  • Racing piston ring kit with pins and circlips
  • Includes a new base and head gasket.
  • NGK CR9E spark plug required 
  • Requires at least 91 octane fuel
  • Requires ECU Flash or other Engine Management (aRacer, etc)


Increasing the compression ratio on the stock bore significantly increases the throttle response and overall power of the engine. In comparison to the stock piston, you can expect more low, mid and top end power while maintaining the use of your stock cylinder. We've designed this piston to be as close to the stock weight as possible without sacrificing any structural integrity. It can clear big valve head with 27/22 valve diameters and it will drop right in to your OEM cylinder. 

You will need either an ECU flash or some sort of fuel controller for this to run properly.

DHM ECU Flash

aRacer Standalone ECU


**Installing this piston requires setting the ring gaps. If you are not comfortable with this, please have your local shop perform the install. Failure to set the proper piston ring end gap can result in premature failure or seizure of the engine. We recommend an end gap of .007-.008" on the top ring and .009-010" on the bottom ring. The silver ring goes on top and the black ring below.