DHM High Compression Stock Bore Piston for the 2022+ Honda Grom / Monkey

DH Motoring

Regular price $120.00

Shipping calculated at checkout.

Customer Reviews

Based on 11 reviews
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Customer

DHM High Compression Stock Bore Piston for the 2022+ Honda Grom / Monkey

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Paul Taylor
Fantastic Service

These folks set the bar fo thier service and help.
I am tearing down my new 2022 Honda Monkey it has me on nerves edge. No manual. I've got a new intake, pistion and cam, along with a new exhaust. Must have sent 20 emails and they helped me out promptly.
Which set my mind at ease. My ECU should arrive at their shop today or tomorrow 5/9/22 for DHM reflash for upgrades. And I have complete faith that all wi go smoothly. I highly recommend this shop for parts
service and support.

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William Callahan
Easy install, simple process, thorough guide.

Very simple process to install new piston. Be careful with your timing cover and timing mark cover do not try to torque just go a good hand tight I cracked mine it's only a 5$ part but a 2 week wait to get. Take your time if you're not sure how to gap the rings, see a local mechanic to have them do it.

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john Jacobs
Not happy

Piston cracked a ring land 200 miles in. Not happy gotta replaced cyl and head now

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Tim Lindemann
2022 high compression piston

Quality piece, reasonably priced and good results. Paired it with the S1 cam, very noticeable gain in overall torque. Highly recommended.

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


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. 

  • ~13:1 compression 50mm stock bore piston
  • 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 base gasket spacer and head gasket (you will reuse your stock base gasket as well)
  • 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.