Does Your New Motorcycle Run Too Lean?

Question: A friend of mine who is a new rider just bought a 2015 Kawasaki Versys 650. So far he loves the bike. Just after the first service, though, talk around the dealership was that he should change the fueling by putting a Power Commander or something on the bike. They say that the Versys runs too lean and that it could run a lot better with some help. He's not so certain.
Joe McCrandall / via email

Answer: It's true that modern bikes run on the lean side of the air/fuel mixture spectrum to help meet emissions. In fact, it's been that way for decades, but the difference now is that manufacturers rely on catalytic converters and oxygen sensors to get to that goal of low emissions without making the bike run poorly. A cat-con burns whatever hydrocarbons don't get consumed in the engine, while the O2 sensor allows the fuel injection to quickly adjust, in real time, to various riding conditions.

But the real issue is to determine if there's a real issue. Does your friend's Versys stumble or surge or run too hot? You'll notice stumbling just as you pick up the throttle. If the engine gasps or hesitates in this transition from off throttle to on, it could be too lean. Surging: If you hold the throttle steady at any given speed, does the bike want to rhythmically speed up and slow down? Does the coolant temperature run above 200 degrees Fahrenheit in stop-and-go traffic? If his Versys is like all the ones we've tested recently, the answer is probably no to all.

Exceptions? When you modify in a way that could change the airflow through the engine—a high-flow air filter element or a full exhaust system, for example. At that point, the stock injection computer might run out of its range during closed-loop running—this is where it’s watching the O2 sensor and tuning on the fly—and will probably not be ideal at engine speeds and loads where the ECU goes into open-loop mode. Bottom line: If your friend’s Versys is running well in the stock configuration, leave it stock.