Honda Grom / MSX Engine goes BOOM! Tuning Tips + What NOT To Do…

– Honda Grom / MSX 125 Blown Engine with Intake & Exhaust | Let’s look at Why it said Bye Bye… –

The Honda Grom took the world by storm back in 2013 and ever since then guys and girls for that matter have welcomed it with open arms when it comes to customizing them. Not only do people attack these 125cc mini-bikes with aesthetic mods, they are also cracking into the engine and throwing big-bore kits, turbo kits (yes, turbo kits!) cams, exhausts, intakes etc on the Grom / MSX 125. Modding the engine on the Grom is the reason for today’s blog post…

Honda Grom / MSX 125 Frame without Engine

An engine is a very complex but simple mechanism in isteslf which is nothing but an air-pump. You want to get air in and out as quickly as possible to put it simply. It’s usually common knowledge that when you are shoving more air in the engine with an intake on the Grom (any engine for that matter) and letting more air out via an aftermarket exhaust on the Grom, you need one more ingredient to finish the recipe and that would be – more fuel! You are altering how the machine came from the factory and Honda has the ECU on the Grom tuned perfectly to pair it up with its stock intake and exhaust, when you go and alter those items, the ECU can only compensate so much for these changes.


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Honda Grom / MSX 125 Frame without Engine

What happens when you make those changes? Well, you run the chance of running too lean. With the engine of the Grom getting more air and letting it exhale quicker thanks to the larger exhaust, you have to throw more fuel at the Grom via some sort of fuel-programmer / tuning device – Examples: DynoJet Power Commander 5 / Bazazz / EJC and you have quite a few other options as well when it comes to tuning your Grom but those brands mentioned are among the most popular here in the USA.

Honda Grom / MSX 125 Engine Blown - Tear-Down / Piston Damage

Honda Grom / MSX 125 Engine Blown - Tear-Down / Piston Damage

Why am I writing this post today about the Honda Grom and tuning it with aftermarket intake and exhaust mods etc? Well… I had a Grom come in our shop with its engine blown. It lasted 9,000 miles with an aftermarket Chimera intake and exhaust system before the engine finally had enough of being starved for fuel while riding at 8,000 RPM rather frequently. With the Honda Grom’s gearing and power-delivery etc it’s commonplace to where you will be running extremely high RPM’s for an extended amount of time. Honda has the most reliable engines in the world bar-none, but when you alter how it came from Honda and then don’t do the needed steps to make sure it’s tuning is on par with how it should be. To where it’s not running too lean or too rich etc then you run the chance of kissing that engine bye-bye earlier than it should have due to pre-mature wear.

What happens when you run your Grom lean by throwing an aftermarket air intake and exhaust etc without adding more fuel? You run lean. What does this mean? Lean means that you’re starving your engine for fuel and in short you’re making your engine work harder and hotter to keep kicking. Fast forward over time, running your Grom engine that lean will = BOOM! Which brings me to the picture below…

Honda Grom / MSX 125 Engine Blown - Tear-Down / Piston Damage

On the Honda Grom forums and Facebook groups etc you’ll find quite a few guys doing plug-chops ad posting up pictures asking “Does my spark plug in my Grom look alright?”. Do you want to trust the livelihood of your engine in the hands of some internet tuning hero? I’m not saying that some guys online aren’t extremely knowledgeable when it comes to tuning and engines etc but do you want to put your engine’s life in a stranger’s hands? All I’m saying is that you need to make sure to do your own research and not listen to what a couple of guys say online. I see this happen daily where people take advice from the incorrect sources and end up paying for it in the longrun.

Sorry for the long-winded blog post covering a topic that I could’ve covered in a lot less words. I just wanted to make it clear that just because your engine on your Grom seems to be running fine with that new intake and exhaust, you could be slowly killing it. If this post helps one person, it was worth it. Thanks for reading as always guys, take care, ride safe and we’ll talk some more soon.

2013 – 2017 Honda Grom Fuel Programmer / Controller / Tuner Options:

Honda Grom Dyno Jet Power Commander (includes MSX 125)

DynoJet Power Commander 5 Description:

The Dynojet Power Commander V is a vital first step into the world of motorcycle fuel tuning. The ability to adjust your motorcycle’s fuel map is vital if you have added a high-flow air filter, aftermarket exhaust system or smog block-off plates. All of these modifications will, in some way, alter the air/fuel ratio in your engine. The Dynojet PCV, with its microprocessors and PCV Software, allows you to adjust your motorcycle’s fuel map to ensure an optimal setting. Dynojet offers a large database of free, downloadable maps for many combinations of motorcycles and aftermarket parts.

If an available map does not suit your specific needs, a custom map can be built from the ground up with the aid of a Dyno. Furthermore, a fuel map can be customized on a per gear, per RPM and per throttle position basis. Both street and track riders will benefit from from the PCV. For example, a daily commuter may find it beneficial to have a low end torque map while the club racer would benefit from a smooth and peak power map.

The Dynojet Power Commander is the most well known fuel controller on the market, thanks for its capabilities and versatility. Take a look around the paddock at a track day, club racing event or AMA event, you will see the Power Commander V dominating the field. Of course you don’t have to be racing your Honda Grom for this to be a worthy investment.

Personally, I use the DynoJet PC5 on my Grom. I’ve had it installed now for almost 3 years. Would I buy it again? Yup. Did it increase the top speed I was able to achieve on my Grom? Yup and I get to sleep better at night knowing she’s not running dangerously lean etc. It was super easy to install too which is a nice thing in the grand-scheme of things as usually when you dive into programmers it can be a difficult task installing them.

DynoJet Power Commander 5 Features:

  • Fuel and ignition timing control USB (Universal Serial Bus) port provides an instant, problem-free way to connect your Power Commander to a computer
  • Provides precise information for fine-tuning a fuel-injected motorcycle when changing an air filter, installing a new exhaust system or doing additional engine performance modifications
  • Each unit includes a built-in microprocessor and a specific map designed to improve engine performance over stock; Dynojet continuously maps new calibrations for each bike, which are available for downloading at their website
  • If you do not have a computer, you can change the settings with three touch buttons on the faceplate
  • OEM-style wiring connectors with improved harness protection are supplied; no wiring modifications required
  • Made in the USA!

Honda Grom Dobeck EJK (includes MSX 125)

Dobeck EJK Description:

Honda GROM MSX125 2014-2015 Fuel Injection Controller, no computer needed. This EFI controller is one of the only ones on the market which allows a large range of adjustability without the use of a computer. We like to use the term ‘on-the-fly’ tuning. You can literally drive the vehicle, make setting adjustments, and instantaneously feel the results. Obviously for safety purposes we recommend you pull over to the side before making adjustments. Some after-market EFI controllers like to claim ‘on-the-fly’ tuning which to them means toggling only between a couple preset maps. The controller actually has 11,390,625 available maps in the unit which are accessible without using a computer program to reprogram the unit. There does exist a computer program called POWERLAB and the controllers can be reprogrammed by a computer, but most users do not require this ability. Why deal with the complexity? It’s an Electronic Jet Kit to make fuel injection tuning easy, simple, and fast so you can enjoy more time riding.

Dobeck EJK Features:

  • No Computer Needed, No Dyno Required
  • Plug-n-Play installation takes minutes to install, all base settings are preset
  • Uses Unique Load Based Technology
  • Offers Full Range Tunability
  • Does Not Interfere with Stock ECU Operation

Honda Grom MSX 125 Engine Blown / Problems - Damage - 125cc Motorcycle / Mini Bike / MSX125 / Grom125


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