Takegawa Superhead 4-Valve 181cc +R Big Bore Kit Honda Grom

Takegawa Superhead 4-Valve 181cc +R Big Bore Kit Honda Grom

SKU #: TKGWA-1001
The ultimate engine upgrade for the Honda Grom 125, Takegawa's Superhead 4-Valve 181cc big bore kit! The Superhead 4V 181cc +R kit makes between 16-18HP! Eliminate the poorly designed OEM 2 valve head the came with your Grom and upgrade to a Superhead 4-Valve! Everything is bolt on ready, no machine work needed!

$1,095.00 Out of stock


Availability: Out of stock

Takegawa Superhead 4-Valve 181cc +R big bore kit has all the important elements to achieve higher performance and more power!


The 4-valve SOHC (single over-head cam) head will open up the engine and allows it to breathe much better than the OEM 2-valve stock head. Takegawa Superhead 4V was designed to accommodate the largest diameter valves that the head could handle, IN: 25mm x2, EXH: 21.5mm x2. This allowing the engine to achieve a high intake and exhaust efficiency! The cylinder is a 63mm diameter, which has been ceramic plated, which in turn will have excellent heat dissipation. The cylinder is equipped with oil cooler ports, which allows you to easily install an oil cooler of your choice (for those planning to install an non-Takegawa Grom specific oil cooler, please see notes below).   


Kit specs and features:

  • 4-Valve Super Head with 25mm intake valves, 21.5mm exhaust valves
  • Center Spark plug placement, which is designed to balance the port shape and achieve high output that could not be achieved with a stock head. 
  • Camshaft has built-in compression release, which makes this kit a +R 
  • Forged Aluminum Roller rocker arms
  • Ceramic plated cylinder wall
  • 12.5:1 Compression ratio (must run premium octane)
  • Built in oil cooler outlets (Note: requires special banjo, please see PN: TKGWA-1010)


Steady Garage R&D:

Additional recommended operational parts:

  • Takegawa High Flow Oil Pump (PN: TKGWA-1005)
  • Oil Cooler (If using the outlet ports from cylinder, PN: TKGWA-1010 is required)
  • Aftermarket Fuel Controller: Bazzaz Z-Fi or Dynojet Powercommander V w/Autotune (for those who don't have access to a dynameter)
  • Upgraded clutch parts: performance clutch springs and/or clutch disc

Optional parts for higher performance:

  • Large Bore or bore out throttle bodies
  • Aftermarket exhaust system
  • Chimera Short Ram Intake System


Professional installation is highly recommended!

Engine break-in, aftermarket fuel controller and special tune/autotune is required! Likewise with any major engine modification or bore up kits, it's now considered a high-performance race engine, extra attention and steps are needed to maintain a high-performance engine.



NO WARRANTY ON RACE ENGINE parts or engine bore up kits.  There is no warranty stated or implied due to the unusual stresses placed on these parts and because we have no control over how they are installed and used.  Steady Garage will not be held liable for any failure or damage caused directly or indirectly from use of these products or engine.  The installation and use of these products or engine shall be conclusive evidence that the user assumes full responsibility for any damage caused directly or indirectly by their use.


This product is legal for closed-course competition use only; for racing vehicles (a competition vehicle not used on public highways). Intended for off-road use or race purposes; may not meet regulations of pollution controlled roads or highways. Not legal for vehicles registered and use in California.