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DHM Honda Grom Stage 3 Package (UPGRADE for prior DHM Customers)


This is the Upgrade kit for existing DHM customers! You MUST send in your previously flashed DHM ecu. If you send in a virgin ECU you will be charged at the full kit price, not the upgrade price. If you do not already own a DHM Stage 1 flash or cam package, do not order from this page. You can order a complete kit HERE.

The DH Motoring Stage 3 Package consists of the following:

DHM High Compression Stock Bore Piston
TB Parts Camshaft
NGK CR9E with spacer

Combined with your aftermarket intake and exhaust, this is the most you can get out of your Grom without doing any head work. After dyno testing we were repeatedly seeing 13.5hp at the wheels (SAE) run after run! The Stage 3 package makes more power than a stock Grom at every RPM and double the horsepower at 9000+ rpm! 91 octane fuel is absolutely required. Any fuel with a lower octane rating may result in engine damage! 

We are not selling preflashed cores as part of upgrade packages. You must send yours in to be updated. This is subject to change, but at the moment there will be no exceptions to this. 

Install video:

Customer Reviews

Based on 17 reviews
Hayden J Murray
Very pleased…. Braaaaaap

Installed the 3 high comp piston days before heading to The Tail Of the Dragon. Already had TB Cam etc. Bike is definitely a lot quicker, holding 55/60 up good grades and 71mph tucked on the flat. Very pleased

Karl Eason (TheReason Motos)
Ready to rip 🤙

David has great customer service, and communication. Product was delivered quickly, accurately and performs as expected and advertised. Thanks!

Jeremy Souza
Wake up the Monkey!

Super happy with the reflash and all the parts, top notch. Assembly and break in was easy and okay. The bike feels completely different performance wise, makes merging and staying up to speed with traffic a breeze. Highly recommend this kit.

Challon Holt
Don't hesitate this upgrade!

I upgraded my cam and immediately felt the power increase. But, it was missing that mid-range "umph". The DHMoto high compression piston delivered that much needed "umph" in a really big way. I have just over 150 miles on it so far and I am super impressed. I had a slight issue when I first installed the piston and David was fast to respond to my email for support. FYI: For those who want to know my issue. You have to use the "stock fuel injector" and not the upgraded PC150.


Zero after purchase support. Everything installs alright, but the flash is garbage and David and his official builder in GA couldn't be bothered to assist. Motor blew in a few hundred miles after continuous reaching out and not receiving any tech support.