DHM 149cc Big Bore Kit for the 2022 Honda Grom

DH Motoring

Regular price $349.00

Shipping calculated at checkout.

Customer Reviews

Based on 12 reviews
tyler adams

Everything’s great BUT Needs to come with stickers lol

Richie Hernandez
Once you go 149, you never go back

All that torque 👌🏻

Travis Goodhile
Great service an parts!

Always a great experience dealing with dhm!!

Very nice torque increase

Already had S1 cam, exhaust and intake on my monkey. Added the big bore kit and reflash of ECU. Only have about 200 miles on it so far. The torque increase is great! Very good quality. And David is very helpful if you have any questions. Definitely run a oil cooler. If this kit does good long term. Which Im sure it will. It will be well worth the upgrade. So far I am Very pleased. Not disappointed at all. In my opinion it's a very easy install. Depends on your mechanichical skill of course. Follow ALL the instructions and recommend add on's. And your sure to have a great experience.

Clayton Morrison
Its great

Very good quality and craftsmanship.it was delivered on time haven't installed yet but if its like the other stuff I've order from dhm it will be great.

After over a year of development, our 149cc kit is ready to go!

Kit includes:

  • 55mm Forged Piston with RK Ring kit 
  • 55mm Sleeved cylinder 
  • Base and head gasket set

This kit provides a significant horsepower and torque increase across the entire rev range. Expect gains of 30% in the midrange over a bike with intake, exhaust and cam, and double the horsepower of a stock bike at 8500rpm.

Our ECU flash or an aRacer MiniX and AF2 combo will be required for proper installation.

ECU Flash located HERE

aRacer MiniX HERE and aRacer AF2 HERE

Extra crankcase vents are also recommended, using either of the following:

AvailMS Cam Cover Vent

MO Power Vented Cam Cover

Install Notes:

  • Two base gaskets included. Use both copper and paper gaskets for pump fuel, use only the copper gasket if you are running race fuel.
  • Oil coolers are highly recommended. Keep an eye on oil temps.
  • An NGK CR9E spark plug must be used
  • Ring gaps must be set during install, we recommend .011" on the upper ring and .013" on the lower ring
  • 91 octane is the bare minimum, and 93 is preferred.
  • When using aRacer, download the quickburn for 149cc + S1 cam
  • Honda injector 16450-KZY-701 is the recommended injector for this kit.


Download setup sheet HERE