Carburetors vs. Fuel Injection

There are a lot of little differences between scooter models. They may not matter to you if you are buying based on price and style. But if you are considering doing you own maintenance, planning to supe it up, or you are interested in being as green as possible, the details about the engine matter. One of those details is Carburetors vs. Fuel Injection, the two common methods for mixing fuel and air as it enters an engine’s cylinder.

The most basic difference between the two methods is that carburetors are mechanical and fuel injection is electronically controlled. Carburetors use the Bernoulli Principal to draw fuel through a “jet” as air is sucked in. Their mechanical nature makes them easy to work on and modify.

Fuel injection systems blow fuel into the cylinder, atomizing the fuel. The amount and timing is controlled by a computer. This means that programming or chips need to be changed to make performance changes. However, the computer control allows for more adjustability. The computer, with its sensors, is better at achieving the perfect air/fuel mixture than a mechanical system. Therefore the mixture burns more efficiently. A fuel injected system is less likely to leave unburned fuel in the exhaust, making fuel-injection the greener choice. The computer can adjust the mixture on the fly with changing conditions, most notably while the engine is warming up. Some carbureted bikes require a manual choke to lean the mixture until the engine warms up, though most modern scooters have at least an automatic choke.

Carbureted engines are simpler and cheaper. Electronic fuel injection improves ease of starting in a variety of conditions, increases dependability, and requires less maintenance. Most manufactures’ websites have specifications online that will list the carburetion/induction method of their models.

4-Stroke vs. 2-Stroke

If you are looking at a smaller scooter, you may need to choose between a 2-stroke and a 4-stroke engine. But what’s the difference, and which one should you get?

The names refer to how many strokes of a piston it takes to accomplish the 4 processes of a combustion engine: intake, compression, combustion, and exhaust. Up and down counts as 2 strokes. The primary difference is that a 4-stroke mixes oil into the engine from a reservoir separate from the gasoline (like your car); while a 2-stroke wants its oil mixed in with the gas (like an old lawn mower). A 4-stroke has to go around again, without firing the spark plug, to draw in the oil and lubricate the cylinder. The 2-stroke, its oil mixed with the fuel, burns that oil. You can smell it and see it in the blue smoke. If you have heard people talk about scooters being bad for the environment… or even the myth that they are worse than SUV’s… those people are talking about 2-strokes. If going green is your thing, get a 4-stroke.

So why a 2-stroke? Well, in a way, it is a more efficient engine. There isn’t that part of the piston’s stroke that is lubricating the cylinder. Therefore, more energy is put directly to drive. A 2-stroke is going to be faster than a 4-stroke of the same size. 2-strokes are simpler and easier to hop-up. If performance is your thing, and you plan to work on it yourself, you are going to get more out of a 2-stroke. But you may need to buy used, as environmental laws have most makers switching to 4-strokes. An exception is the 2008 Zuma by Yamaha.