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DHM 149cc Big Bore Kit for the 2022+ Honda Grom/Monkey (Gen 2)

$349.00
by DH Motoring

Our second generation 149cc kit is now ready to go! We've made a few updates to make the install process easier and more simplified. We've also eliminated any potential clearance issues and streamlined the manufacturing process even further to help pass on savings to the customer. 

Generation 2 updates:

  • Wider skirt bridges for more squirter clearance
  • One additional oil control ring lubrication hole compared to the previous piston
  • Two additional piston skirt lubrication holes compared to the previous piston
  • Compression on pump gas is now 12:1 to reduce detonation when hot

Kit includes:

  • 55mm Forged Piston with ring kit
  • 55mm Sleeved cylinder 
  • Base and head gasket set

This kit provides a significant horsepower and torque increase across the entire rev range. Expect gains of 30% in the midrange over a bike with intake, exhaust and cam, and double the horsepower of a stock bike at 8500rpm.

Our ECU flash or an aRacer MiniX and AF2 combo will be required for proper installation.

ECU Flash located HERE

aRacer MiniX HERE and aRacer AF2 HERE

Required supporting mods other than the ECU tuning include an DHM S1 or DHM S1R camshaft, oil cooler kit, crankcase vent and fuel injector. We have options listed below:


Injector: PCX150 Injector

Starter (optional but recommended): CJR Performance HD Starter

Spark plug: NGK CR9E

Install Notes:

  • Two base gaskets included. Use both the OEM Honda base gasket and the grey paper gasket for pump fuel setups, use only the OEM Honda base gasket for race fuel.
  • Oil coolers are required. Keep an eye on oil temps.
  • An NGK CR9E spark plug must be used
  • Ring gaps must be set during install, please see the setup sheet for further info.
  • 91 octane is the bare minimum, and 93 is preferred.
  • When using aRacer, download the quickburn for 149cc + S1 cam
  • Honda injector 16450-KZY-701 is the required injector for this kit.


Download setup sheet HERE


Installation:

Customer Reviews

Based on 45 reviews
80%
(36)
7%
(3)
7%
(3)
2%
(1)
4%
(2)
J
Jose Rivera
149cc Big bore kit

I installed it with a chimera intake. Aftermarket exhaust. Its smoking a lot. Took it apart again made sure the oil rings didnt slip out. Put it back and it's still smoking. Maybe im doing something wrong. Runs super smooth love the new sound!!!!

R
Ruben Hernandez
149cc bbk

it's a 4/5 because of customer service not because of the kit
i'm running this on a trail 125
it's honestly pretty solid
i have been running the cam for a little bit now and decided i need a little more nuts on it and it delivered
i'm going 65 with an upright seating position
the customer service has been lacking on this but it's cool
lately everyone has kind of been wack

i did not get a tune from them i did buy an afr module and aracer from them a while back
you could use the grom tune if you don't wanna spend almost a thousand getting the afr and aracer
the idle after letting off is a little higher and i'm not sure if it's because i'm in arizona it throws a code for temp at 245-250
the trail was already running that hot from factory and didn't throw a code for over temp
but that's not because of the bbk that's probably because the grom runs cooler so the tune is for a grom

C
Charles Gervais

Bike run great lot of Power but Little lag or hésitation at low rpm! ITS like bike run on/off !

E
Elmer Williams
149cc BBK - Wow, just enough to make it feel like a real bike.

David and his staff went up and above on customer service. They answered all my questions, communicated promptly and shipped quickly. I paired the 149 BBK with chimera intake, dhm s1 cam, speed pro cam sprocket, kitaco hv oil pump, kitaco 5 row oil cooler, 60% clutch springs, avail cam vent adapter, 14/37 gearing, yumanashi 4th bearing, pcx150 injector, and dhm flash. This thing rips now. Feels kinda like a real bike haha. I bought the koso 34mm throttle body.and intake, but am waiting for the ported head to get back in stock before i install it all...cant wait. Thanks DHM!

K
Kevin Lundquist
Impossible to put on

They tout this as easy to install. The piston rings would not go on and I’m pretty much stuck with a broken bike

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