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Core ECU

**Mail-in ECU turnaround time is only 1-2 business days!

***Once you've completed checkout, you will receive the shipping info as well as a link to a form so you can list your exact modifications. Each tune is tailored to your exact modifications!

DHM is here to offer you the original flash tuning solution for the Honda Grom / Monkey! Our stage 1 software cleans up the air/fuel ratio and optimizes ignition timing among many other tables for bikes with nearly any modifications. 

Looking at the dyno graph, you'll see the blue and green lines that are the graphs for the stock, unmodified ECU. It runs extremely lean up top and therefore only makes around 6-7HP at 9200rpm. By controlling the air/fuel ratio we're able to extract up to 3HP more in the higher RPMs. The peak number is only about 1hp but in a race on the street the tuned bike will continue to pull gear after gear because it does not lose power after 7,000rpm.

Our ECU flash not only increases horsepower, but it also makes the engine run safer now that it has adequate fueling.

***This is the best alternative to a fuel controller, especially at the price point. You no longer need to spend hundreds of dollars on a tuner if you only have simple bolt-ons on your bike. If your bike is running a modified intake and exhaust this is your ticket to a smooth running bike with OEM like ride-ability. Since we retain the stock ECU, the bike will start, run and idle like normal, but will produce more and safer power throughout the rev range.

***Each tune is catered to your exact modifications (intake, exhaust and cam brands, etc.) After checkout you will receive a link to an online form that will ask for your bike's exact setup so we can tune it accordingly.

We have maps for pretty much every intake, exhaust and cam that is available on the market. 


  • Up to a 3HP gain at high rpm compared to an untuned ECU!
  • Raised rev limit of 10,000rpm (compared to 9250rpm stock) higher limits available upon request
  • Corrected air/fuel ratio
  • Additional ignition timing advance for improved throttle response and power
  • Revised fuel injection timing for better atomization
  • Higher top speed
  • Better mid range and torque
  • Optional tip-sensor delete
  • Optional cold-start high idle delete
  • Optional closed loop delete (will allow your piggyback to make changes to the closed loop portion of the map)

Available Tunes:

  • Stage 1: Intake and Exhaust mods
  • Stage 2: Intake, Exhaust and Cam
  • Stage 3: High Compression Piston, Intake, Exhaust and Cam
  • Custom: Contact us for custom setups!

For big bore tuning, click HERE

How to order: 

You can mail us your ECU and we will flash it and get it back in the mail by the following business day (1-2 day turnaround time). (After checkout you'll receive an email confirmation with shipping instructions.

If you do not wish to have the downtime, we can provide a core flashed ECU to you. You will have to pay a core charge ($95 for SF and Monkey, $110 for OG) which will include a preflashed ecu. You can choose to return your stock ecu for a $50 core refund after you've received the new one.  

If we revise your current setup's tune in the future we will update your ECU for free (you just pay shipping both ways). If you'd like to update to a different setup later on (big bore, cam, etc) we only charge a $35 upgrade fee which includes return shipping to you as well.

Customer Reviews

Based on 324 reviews

Fast turn around and amazing tune. Totally worth it.

Craig Thompson
Ecu reflash

Great upgrade. It has a lot more pep mid to high rpms.

Ethan Harris
Very impressed! 10/10

Ive been riding my 2018 grom with a DIY airbox mod since i got it, then shortly later added a zoom loop exhaust. Noticed an increase in the top end of the powerband just from that alone, and rode it around like that for about a year. Just received my stage 1 flashed ecu from DHM yesterday and put it on. At first while the ecu was still learning the new tune, i was almost a bit disappointed in the high rpm performance (only rode it about 5-8 miles yesterday) WELL today i went for a ride with a group of friends and ended up putting about 70 miles on it. Let me just say, after about 35 miles, I could absolutely feel the bike coming alive above 7k. It just feels like the bike WANTS to get to redline now and its an absolute blast. Plus the peace of mind knowing my AFR is sorted out as well is just the cherry on top. I would definitely recommend this to anyone running an intake and exhaust. Very pleased with my purchase! Thanks DHM!

Tanner Huddlestun
Ecu reflash

Very pleased with reflash , bike runs a lot better and is a noticeable difference on power.

Nate Tomkins
Grom tune

Did a tune for intake and exhaust definitely woke the bike up and can tell a difference highly recommend quick turn around time