Two Strokes Or Four? Choosing The Right Engine For Your Motorized Bike

Motorized bicycles combine the best traits of a bicycle with those of a standard moped, making them extraordinarily versatile and easy to use. The best part is that the components for a motorized bike, including the engine, gearbox, and other hardware, can be added onto your existing bike.

While there are plenty of electric-powered bikes out in the wild, most motorized bites come in two-stroke or four-stroke flavors. If you can't decide which type of engine you should choose, just take a look at the in-depth guide below.


Two-stroke engines tend to be cheaper and easier to maintain thanks to their design, which features fewer moving parts and the less complicated combustion process than a comparable four-stroke engine. However, two-stroke engines still require slightly more short-term maintenance than their four-stroke counterparts. Two-stroke engines also tend to have a shorter lifespan than four-stroke engines.

Another downside of a two-stroke motor is that it requires users to pre-mix gasoline with two-stroke oil prior to fill-up. This helps minimize wear and tear on the piston and cylinder liner. Mixing fuel and oil can be time-consuming, plus it's easy to get the mixture wrong if you're not careful. In contrast, four-stroke engines don't need oil mixed with their fuel since there's already a reservoir that can be filled with oil for lubrication purposes.

Riding Style

If you plan on taking your motorized bike out on the trail, then you'll need an engine that offers plenty of low-end torque. This is where a four-stroke engine excels, as it can smoothly generate plenty of low-end torque at slower speeds. Four-stroke engines also tend to use fuel more efficiently, which means you'll get more mileage out of your four-stroke engine then you would with a comparable two-stroke engine. 

A two-stroke engine, on the other hand, offers better top-end power delivery. Most two-stroke engines also offer higher top speeds than their four-stroke counterparts, making them ideal cruisers for high-speed commuting. It's also worth noting that two-stroke engines are usually louder than comparable four-stroke motors, making it essential to have a muffler when riding in residential areas.

If you want to buy a motorized mountain bike, keep these things in mind.

Startup and Take-Off

Most four-stroke motorized bicycle engines offer a pull-start system similar to those found on lawnmowers and other gas-powered lawn care equipment. These engines also feature a centrifugal clutch for easier startup. Once you pull the rope or cable to start the engine, all you need to do is crack the throttle and let the revs build before taking off.

Startup and take-off on a two-stroke motorized bicycle is a bit more complicated. You'll first need to pedal under your own power up to a sufficient speed, usually around 5 mph, while holding the clutch in. Once you're up to speed, you can release the clutch to allow the engine to engage. You also need to adjust the carburetor settings to ensure the engine will start beforehand.


With fewer moving parts and simpler designs, the average two-stroke motor tends to be lighter than comparable four-stroke engines. If you plan on keeping your mountain bike as light as possible, then you may want to consider a two-stroke engine instead of a slightly heavier four-stroke design.


The average cost of two-stroke and four-stroke engines can vary due to a variety of factors, including engine size, build quality, modifications, and accessories. The relative simplicity of a two-stroke engine tends to make one more affordable than its four-stroke counterpart.

In short, two-stroke engines offer excellent affordability, simplicity, and top-end power. Meanwhile, four-stroke engines offer better low-end torque, better longevity, lower noise and vibration, and better fuel economy. Armed with this information, you'll be able to choose the right motor that best fits your bike.