Science & Technology

How to turn your old bike to a mean machine with a two-stroke or four-stroke engine

Will this be the future of riding bikes?

Louder than a car, faster than a electric scooter–what can it be? Just me on my motorized bike, passing cars, skirting through the city like a breeze. I can go anywhere, any time, and within minutes, I’ll be there. It took some work to convert my bike, but now,it’s awesome.

Electric bikes may be what people are getting around on theses days, but internal combustion engine bikes are a lot more fun. Sure, electric bikes are efficient, quiet, reliable, long lasting, and have a decent amount of riding time, and yes, fuel-powered motors do require more maintenance, but these bikes are fast, and don’t require any charge.

Before I go any further, I should warn you that the two-stroke and four-stroke engines used on for motorized bikes are regulated strictly. Engines that are above 50cc are illegal in North America. You also have to keep your speed under 45 km/h (28 mph). And no one under 14 is legally allowed to operate a motorized bicycle. (That said, under-aged motorized bicycle riders have been known to simply turn off the engine when police are nearby, and get away.) Two-stroke and four-stroke engine kits are sold online for $125 to $500 Canadian.  They come in sizes from 39cc to 80cc. Cheaper engines are usually not very good quality, and can have problems with the clutch, throttle, carburetor, piston and, spark plug. Expensive engines comes with a more advanced carburetor, engine, throttle, and clutch.

The kit comes with a spark plug, chain, chain tensioner, capacitor discharge ignition (CDI), cables, throttle, sprocket, carburetor, clutch, exhaust and spare parts (bolts and nuts). A CDI is almost like a car battery, it contains electricity which is wired to the coil which powers the magnet to spin, the magnet creates a spark and ignite the the chamber, giving power. With no spark means no power–I found that out the hard way.

Two-stroke engines requires you to mix “synthetic two-stroke oil” just you would with a lawn mower or chain saw. The engine will take a 16-1 ratio of gas to oil for the break-in period. It will always run better with the “Premium” gasoline. Engines take 300 miles to fully break-in. After the break-in period you will need to change the ratio to a 25-1 mixture with gasoline.

In two-stroke engines, a single piston is moved by crankcase. The crankcase rotates. Every half turn it pushes the piston up the cylinder or brings it down. Each time the piston is forced up, it hits the spark plug causing the cylinder to ignite. This brings power to the engine. Two-stroke engines are usually more powerful than a four-strokes, depending on the size.

The benefit to four-stroke engines is that they are more efficient on gas, and you do not need to mix gas with oil which is a lot less work and money. Plus you can fill it up at any gas station if you’re ever low—no need carry around a jerry can.

Four-stroke engines are very reliable, but if they do break they are very difficult to fix and cost a lot more. They work like this:

There is one piston in the cylinder. When the piston moves up and down the cylinder it closes the the intake which causes it to touch the spark plug and ignite the cylinder. This is called the compression stroke–when the fuel ignites, it pushes the piston back down the cylinder, this causes the bike to engage and start running–this is called the power stroke. The exhaust releases when the piston travels back up the cylinder. It all comes out the exhaust port leading to the exhaust. This process repeats extremely fast

If you are looking into putting a motor on a bike, make sure the bike is right. The bike frame will need to be a big enough diameter for the engine. Also, I recommend purchasing one that is $200 or more. Buying a cheap bike was my mistake. The engines put out a lot of power and you need decent quality gears to hold up. If the clutch gearing system wears down, it will leaving it loose and noisy when you ride.

The aftermarket parts are inexpensive but you can pick yourself up the full clutch kit for little as $35, including everything you will need to fix your bike. Almost every part you can break can be purchased on Amazon or any other motorized bike website.

So if you’re looking into buying a motor for your bicycle, make sure you’re definitely interested because it can be a bit of a headache trying to figure it out. But if you are willing to put the effort in, zipping around town on a motorized bike is a lot of fun.

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