ASK THE MXPERTS: FUEL INJECTION VS. CARBURETED FOUR-STROKE

FUEL INJECTION VS. CARBURETED FOUR-STROKE

Dear MXperts,
When my 2003 YZ250F blew up, my friend let me ride his 2020 YZ250FX. It was like riding a Cadillac. Honestly? It felt kinda slow, because it was smoother. I’m not an experienced rider, but was still riding fast enough to tell the difference. Is fuel injection slower or am I?

Here are the historical facts that support your claim that fuel injection isn’t as good as a carburetor, power-wise. Although most people are tempted to believe that fuel injection was the most important change on the 2009 CRF450, the MXA wrecking crew wasn’t the least bit enamored with the first year that the CRF450 was fuel injected. That was the model year when fuel injection could be directly compared to carburetion on the Honda CRF450. In MXA’s opinion, back in “year one” of EFI, fuel injection was not better than a well-jetted carburetor. EFI didn’t hit as hard in the middle, make as much horsepower on top or deliver excess fuel (when excess fuel was called for). It was just another way to get gasoline into the combustion chamber.

Of course, once Honda applied more technology to the fuel-injection system, they ironed out the bugs, but the lesson had already been learned.

Today, the fuel-injected 2025 KTM, Husky and GasGas two-strokes are decidedly slower-feeling than the 2022 carbureted models they replaced. In fact, in MXA’s “2023 125 Shootout,” the Keihin carb-equipped 2023 GasGas MC125 blew the updated and fuel-injected KTM and Husky models off the track. The Keihin carb made it easier to get on the pipe out of corners and allowed our test riders to over-rev the two-stroke engine far past the limiter on the high-tech KTM and Husky EFI models. At the 2025 World Two-Stroke Championship, 125 Pro winner Josh Mosiman raced the same KTM 125SX that he raced back at the 2022 World Two-Stroke Championship. Why did he run the old bike? Because it had an Electron carburetor.

All of that info doesn’t mean that fuel-injected bikes aren’t worthy race bikes, just that on feel alone a carb is not at a disadvantage—save for the fact that bikes that come with carbs don’t get any updated mods like the electronic trickery that comes with EFI models.

The big plus of fuel injection is that it is hands-off. There is no need to re-jet for altitude, temperature or humidity, because there are no jets. We knew even back in 2009 when we raved about the better performance of the carb on the 2009 CRF450 that EFI would eventually replace carburetors and beat them in performance, but that wasn’t going to happen in 2009.