DHM Performance ECU Reflash – Honda Grom & Monkey (2014–2020)

Mail-in ECU turnaround: 1–2 business days. After checkout you’ll receive shipping instructions and a link to submit your exact modifications — every tune is built specifically for your setup.

DHM ECU Reflash – Honda Grom & Monkey (2014–2020)

The original and most trusted ECU flash tuning solution for the Honda Grom and Monkey. DHMotoring has tuned over 10,000 ECUs and holds maps for virtually every intake, exhaust, and cam combination on the market. No piggyback controller needed — just a cleaner, safer, more powerful tune on your stock ECU.

Stock Groms run dangerously lean at high RPM, capping out around 6–7 HP at 9,200 rpm. DHM’s reflash corrects the air/fuel ratio, advances ignition timing, and raises the rev limit — unlocking up to 3 additional HP at high RPM while keeping OEM-like driveability and reliability.

Performance Benefits

• Up to +3 HP at high RPM vs. an untuned ECU
• Raised rev limit to 10,000 rpm (stock: 9,250 rpm) — higher limits available on request
• Corrected air/fuel ratio for safer engine operation
• Additional ignition timing advance for improved throttle response
• Revised fuel injection timing for better atomization
• Improved mid-range torque and top speed
• Optional tip-sensor delete
• Optional cold-start high idle delete
• Optional closed-loop delete (allows piggyback controllers to modify the full map)

Available Tune Stages

• Exhaust Only — Optimized for bikes running an aftermarket exhaust only
• Intake Only — Optimized for bikes running an aftermarket intake only
• Stage 1: Intake & Exhaust — For bikes with aftermarket intake and exhaust
• Stage 2: Intake, Exhaust & Cam — Adds camshaft tuning on top of Stage 1
• Stage 3: High Comp Piston, Intake, Exhaust & Cam — Full bolt-on performance tune

Core ECU Options

• Send your ECU in — Flash and return within 1–2 business days
• OG Core (2014–2015) — Pre-flashed core ECU; return your stock unit for a $50 refund
• SF Core (2017–2020) — Pre-flashed core ECU; return your stock unit for a $50 refund
• Monkey Core (2018–2021) — Pre-flashed core ECU; return your stock unit for a $50 refund

Future Updates

If DHM revises your current setup’s tune, your ECU will be updated for free (you pay shipping both ways). Upgrading to a different setup (big bore, new cam, etc.) is only a $35 fee, including return shipping.

Running a big bore kit? See our DHM 186cc ECU Reflash instead.

Fitment

• Honda Grom OG (2014–2015)
• Honda Grom SF (2017–2020)
• Honda Monkey 1st Gen (2018–2021)