We are proud to introduce the first "all inclusive" big bore package for the Honda Grom! Fits 2014-2020 4-speed engines ONLY.

The DHM 186 kit includes everything you need to convert your Honda Grom in to a big bore machine. You no longer have to piece parts together with expensive components to get more power out of your bike. Our kit utilizes hardware from TBParts along with an OEM Honda injector and our software tuning to create a reliable and powerful kit that makes the Grom easier and more fun to ride.

Included:

186cc Cylinder and Piston
Complete Oil Cooler Kit
OEM Honda PCX150 Fuel Injector
DHM Reflash
TB Camshaft or Decha HR Camshaft (you can select an option to reduce the price if you already own one)
TB Oil Cooler or Drow Sports Juggernaut high mount cooler

Performance Data:

16.5 HP and 14.5 Ft/lbs of torque! A gain of 74% in HP and 67% in torque over a stock bike. (Dyno chart available in photos above)
20-50mph in 5 seconds compared to a stock bike at 9 seconds

Options:

TB or Decha HR Camshaft. This kit is designed to be run with the TB or Decha HR camshaft. If you already have one, you do not need to select it. If you do not already own one, please add it by using the drop down menu when ordering.

Choose between a TB Parts Low mount cooler (pictured) or a Drow Sports 7-row black high mount cooler

ECU Flash Options:

Mail your ECU in and we'll flash it and send it back with the kit
Purchase a new pre-flashed ECU that will be shipped with the kit
Purchase the DHM Flashing Suite Cable that allows you to flash your ECU at home using your Windows PC / laptop.

Since our primary business is building race engines, we take a lot of pride and care in our engine assembly. Before shipping, we will check all ring gaps, and we will also align the rings in the piston and install the piston in to the cylinder for you with the alignment we recommend!

**An upgraded intake and exhaust are not required but are highly recommended!

Completely upgradeable:

Since we are flashing the OEM ecu, you can still use piggybacks on top of this kit should you decide to make any changes. If you would like to add a big valve head or change the cam, etc., you can do so and use your piggyback fuel controller (pcv, etc) to tune it as you normally would. The fact that we've reflashed the stock ecu for fuel and timing will actually provide a better base than the stock, unmodified ecu!

***Requirements and General Information:

The ECU reflash requires your stock narrowband O2 sensor to be installed and plugged in. If you have removed this to use another fuel controller, you will need to reinstall it. The ecu will learn and adapt over the first 15-20 miles, so acceleration and overall ride ability will increase up to that point.

Installation instructions are not included. If you are not capable of working on these engines, having a shop perform the install is recommended.

This kit is designed to be bolt-on, reliable power. However, at the end of the day the Grom engine is a very simple air-cooled engine, and heat is the enemy. If you plan on taking regular highway trips, an oil temperature gauge is highly recommended to make sure the engine does not overheat. OPMID and Koso both offer great options.

DH Motoring All Inclusive Big Bore Kits