Top 10 Honda Grom Modifications

Troy Siahaan
by Troy Siahaan

Here at MO we like riding slow bikes fast. Both Chief Editor Duke and contributor Gabe Ets-Hokin have written columns about it (read Duke’s here and Gabe’s here), but it’s a sentiment all of us on staff share. To prove it, I’ve signed up the entire staff, sans Tom (he’s got a press intro to attend. Ppfff), to come race with me in a 24-hour race on mini bikes, organized by the United Mini Racing Association. Our chariot that will hopefully lead us to glory (embarrassment, more likely)? None other than the hugely popular Honda Grom.

While never intended to be a racing machine, the Grom aftermarket has gone wild with ways to transform Honda’s little funster into a weapon capable of terrorizing a racetrack. What follows are 10 upgrades we’re throwing onto our Grom that will not only give us a shot at running at the front, but also help the Grom survive 24 hours of abuse. All told, the following list represents $4,564.22 in aftermarket parts (and this isn’t even everything we have), more than $1400 more than the bike itself! Stay tuned, as we’ll be documenting the installation of many of these parts in a later story.

10. SBS Sintered Brake Pads/Spiegler Steel-Braided Brake Lines

We begin this list of go-fast parts for the Honda Grom with two items crucial for slowing down: brake pads and steel-braided brake lines. Since our beloved play bike was never meant for high-performance applications, it suffers from stopping power that feels like two pieces of wood clamping down on the disc (although it’s oddly consistent lap after lap), and a spongy lever. Thankfully, both items are easily solved via the aftermarket. SBS sent us its 797RSI sintered pads for the Grom, which should provide greater stopping power, be able to last the whole 24 hours and still provide significant more feel over the stock organic pads. They can be found for around $30 online.

Of course, a good set of pads is almost a waste without steel-braided lines, and the folks at Steady Garage hooked us up with the Spiegler brake line kit specifically for the Grom. For $125, the kit includes both front and rear lines along with all the necessary banjo bolts and crush washers for the job. The result should be much improved and consistent feel at the lever, lap after lap.

9. Woodcraft Rearsets

When lean angles are what you’re trying to improve upon, the standard pegs put an end to that task fairly quickly. Sure, the stock position is comfortable for a trip around town, but at the racetrack they severely limit ground clearance. Enter Eric Wood and these Woodcraft rearsets, specifically for the Grom and distributed by Todd Robinson at Blue Monkey Motorsports. Available in both standard and GP shift, the $429.99 kit includes a set of rearsets constructed from 6061 aluminum, separate peg, shift and brake levers, and the associated hardware needed to install everything. The pegs themselves are adjustable to two different positions, both of which provide significantly more ground clearance than the stock pegs. And because the rearsets are made in America, replacement parts are easy to come by.

8. Kuni Adjustable Levers

When you have five riders racing the same bike, making the bike as adjustable as possible to suit the different riding styles is important. Since the Grom is fitted with non-adjustable brake and clutch levers, we’re swapping them out for these $35 Kuni levers, courtesy of Steady Garage. They aren’t shorty levers, nor do they fold in the event of a fall, but they do provide six-way adjustability and the tips are hollowed to minimize damage should the lever touch the ground.

7. Takegawa Hi-Flo Oil Pump

Leave it to the Honda Grom forum to bring to my attention something I hadn’t considered. Because the Grom’s 125cc engine is air-cooled, it relies on oil to help cool things down. The stock oil pump is adequate for the task Honda designed the bike for – an around-town errand runner – but when it comes to sustained high rpm racing, the stock oil pump is taxed to its limit. Enter Takegawa and its Grom-specific high-flow oil pump. As the name implies, the high-flow pump is claimed to increase oil flow by as much as 35% over the stock unit. For $57, we consider that cheap insurance, especially for a 24-hour race.

6. Morin Oil Cooler

Now that we have a high-flow oil pump, we’re going to take full advantage of it by adding a Morin oil cooler to help prolong engine life even further. The $168 Morin Complete Bolt On Oil Cooler Kit also comes courtesy of our friends at Steady Garage, and comes with everything needed to install the kit, including oil cooler, bracket, lines with AN fittings, and all the necessary bolts, including an extended head stud that will allow the oil to flow from the cylinder oil passage to the cooler. The cooler installs directly in front of the cylinder head, and the protective grate in front of the cooling fins helps protect against debris the front tire might kick up. How much impact does the cooler have? Some reports on internet message boards have shown as much as a 30-degree variance in oil temps with and without a cooler.

5. Suspension

Second to the Grom’s lack of power is its woefully under damped suspension. Designed to be affordable and comfortable on the street, they are far too soft for track duty. We’re fixing that with the help of a JRi double adjustable shock and K-Tech’s fully adjustable fork upgrade kit. The $699 JRi shock is fully adjustable for compression damping (high- and low-speed), rebound damping and spring preload, and is currently the only rear shock upgrade for the Grom available with ride height adjustability. As an added bonus, each JRi shock is manufactured to the specific needs of its rider.

Up front, the $549.95 K-Tech fork upgrade kit also features compression, rebound and preload adjustability, making it the only Grom fork kit on the market today with fully adjustable capabilities. The kit also comes standard with 6.5Nm springs (stock is 5.0Nm) to help firm up the ride, but 6.0Nm and 7.0Nm springs are optional. Fork shafts are hard chrome plated for strength and wear resistance, while internal aluminum fork components are hard anodized to resist contamination. To top it off, the top caps are CNC machined aluminum.

4. Intake

When it comes to adding power and going fast, we trust Brock Davidson and Brock’s Performance. In fact, Brock has a whole page on his website dedicated to Grom go-fast goodies, and one of those bits is this ram air intake kit which replaces the restrictive stock unit. The $169.95 kit includes a Sprint Filter waterproof conical air filter, Chimera ram air intake pipe and all the necessary hardware for a proper install. It’s a direct bolt-on kit, and the beauty of the Sprint Filter is it only requires compressed air for cleaning, no washing and re-oiling necessary. According to the Brock’s Performance dyno, this kit netted a jump in horsepower from 10.31 hp to 11.47 hp, and an increase in torque from 8.10 lb.-ft. to 8.65 lb.-ft. on their test bike. Those numbers may sound small for those used to triple-digit figures from big bikes, but that’s a whopping 11.3% gain in horsepower and an equally impressive 6.8% increase in torque.

3. Alien Head Full Exhaust

What good is an intake kit without an exhaust to match? Fortunately, Brock’s hooked us up with one of his Alien Head full exhausts, too. Available in either polished ($399.95, shown above) or black ($499.95) versions The 12-inch megaphone muffler features a 2-inch outlet for increased exhaust flow and a deeper sound. It’s also designed to work with the stock foot pegs and provide maximum ground clearance for those who’d rather stretch and lower their Groms. Since we’re more concerned with performance in this application, let’s talk numbers. According to the Brock’s Performance scales, the stock Grom exhaust system weighs 11.0 lbs. The Alien Head system? A mere 4.15 lbs. That’s a 63% weight savings. As for power, the Alien Head system made 10.07 hp (vs. 8.57 hp) and 8.17 lb.-ft. (vs. 7.85 lb.-ft.) on Brock’s test bike. That’s 17.5% more power and 4.1% more torque. We’ll gladly take those gains.

2. Power Commander V

Of course, if you’re going to make a motorcycle breathe easier, it’s best to give it a revised air/fuel mixture to extract the most power. This is where the Power Commander V comes in. Also provided to us from Brock’s Performance, the $399.95 PCV is less than half the size of the Power Commander III, with more functionality. While the capabilities of the PCV are far greater than the capabilities of the Grom, it’s nice to know the PCV is able to map each individual cylinder in each gear on a multi-cylinder motorcycle. It also allows the user to adjust timing +/- 20 degrees, no longer needs a 9-volt adapter, has a built-in, two-position map switching function, and even comes with pre-installed street or race maps if you buy it and an exhaust system from Brock’s.

1. BST Carbon Fiber Wheels

Definitely the single item for our Grom we’re most excited about testing are these carbon fiber BST wheels, provided to us by Brock’s Performance, as you can see in the sticker. At $1500.83 (no, that’s not a typo), the BST wheels are almost half the cost of the bike itself. However, there’s no arguing the dramatic decrease in weight – approximately 2 and 3 lbs. lighter, respectively, from the stock 6-lb. front and 7-lb. rear. That’s a significant drop in weight to be sure, made more so by the fact the drop in rotating mass will greatly benefit every performance aspect of the bike. The wheels are available in two sizes; OEM sizing (2.75-inch x 12-inch front, 3.5-inch x 12-inch rear) or a wide option, which includes a 140/70-12 rear tire (instead of the standard 130/70-12) mounted on a 4.0-inch x 12-inch wheel. A 120/70-12 front tire is standard on both.

Speaking of tires, sharp eyes will notice the Michelin Power Pure SC rubber mounted to our wheels. They offer sticky edge grip plus exceptional durability, thanks to their dual-compound design – Michelin says they are the only dual-compound scooter tire on the market. If ordering tires with wheels from Brock’s, they are shipped mounted and balanced, plus they can be inflated with temperature-stable nitrogen instead of regular air. Were you to buy the tires separate from the wheels, it would cost you $73.95 front and $77.95 for the 130/70-12 rear. Add two more dollars for the 140-rear.

Troy Siahaan
Troy Siahaan

Troy's been riding motorcycles and writing about them since 2006, getting his start at Rider Magazine. From there, he moved to Sport Rider Magazine before finally landing at in 2011. A lifelong gearhead who didn't fully immerse himself in motorcycles until his teenage years, Troy's interests have always been in technology, performance, and going fast. Naturally, racing was the perfect avenue to combine all three. Troy has been racing nearly as long as he's been riding and has competed at the AMA national level. He's also won multiple club races throughout the country, culminating in a Utah Sport Bike Association championship in 2011. He has been invited as a guest instructor for the Yamaha Champions Riding School, and when he's not out riding, he's either wrenching on bikes or watching MotoGP.

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8 of 24 comments
  • Old MOron Old MOron on Sep 13, 2015

    Well, I got up at 05:00 to watch the Moto GP race. That was very dramatic and entertaining. Now I'm trying to piece together how our MOrons did in the 24-hour race.

    Looks like they started off pretty okay. They were losing about 5 seconds per lap to the fastest teams. They were doing about 42 laps/hour, and the fastest teams were doing about 49 laps/hour. After an hour and a half, they were down by 10 laps.


    But after almost six hours of racing, the MOronic lapping rate had deteriorated. They were now running at 35 laps/hour, while the fastest team was at 48 laps/hour.


    After 8 hours of racing, the MOrons were doing 33 laps/hour, while the fastest team remained at 48 laps/hour.


    Skip ahead to almost the end of the race. With about an hour and a half left to go, the MOrons were running at 40 laps/hour. The leading team was doing 46.5 laps/hour.


    Hmm, overall the MOrons and the winning team began and ended the race pretty consistently. But somewhere between hour 2 and hour 8, the MOrons must've had an issue. Oh well, I bet it was fun for them, and it was interesting for me to follow.

    • See 3 previous
    • Kevin Duke Kevin Duke on Sep 15, 2015

      We can't blame any of it on JB! We forced him to stay at home to write most of our big adventure shootout and to avoid putting his fragile old body under threat from a small motorbike. :)

  • Don Avant Don Avant on Oct 12, 2016

    RE: "should provide greater stopping power" and " should provide greater stopping power "

    This article would be MUCH MORE USEFUL If it was written after these were installed and tested...Also, are you getting any monetary renumeration for pimping these products ? A negative answer would boost your veracity