How to Convert Your Electric Bike to Gas Power

Converting your electric bike to gas power is possible, but it requires mechanical skill and a willingness to replace most of the electrical system with a small gas engine kit. The process involves removing the battery, motor, and electronics, then mounting a 49cc or 80cc two-stroke engine, fuel tank, and drivetrain to the frame. Expect to spend 6–10 hours on the work and under $200 on a basic conversion kit. Below is a step-by-step guide.

Step 1: Choose a Bike That Can Handle the Change

Not every e-bike frame is a good candidate for a gas conversion. The engine and fuel tank add roughly 15–20 lb, and the vibration from a two-stroke can loosen brackets over time.

• Frame strength: Steel frames are best; aluminum frames can work if the downtube is thick-walled. Carbon fiber frames are not suitable – drilling or clamping can cause structural failure.
• Wheel size: Most conversion kits fit 26″ or 700c wheels. Fat-tire bikes (4″+ tires) often have wider bottom brackets that may not clear the engine sprocket.
• Brakes: Disc brakes are preferred over rim brakes because gas bikes can reach 30+ mph. If your e-bike has rim brakes, plan to upgrade to a disc brake system on at least the front wheel.
• Suspension: Full suspension e-bikes are harder to convert because the engine mount must avoid rear swingarm movement. A hardtail (front suspension only) is much easier.

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Step 2: Select a Gas Conversion Kit

The most common kits are two-stroke engines in 49cc or 80cc. Four-stroke kits are quieter and more reliable but cost twice as much and weigh more.

Your kit should include:

• Engine with carburetor and exhaust
• Mounting bracket and hardware
• Drive sprocket (often a 44-tooth) and chain
• Fuel tank (usually a small plastic tank that mounts between frame top tube and handlebars)
• Twist-grip throttle cable assembly
• CDI ignition and spark plug

Avoid kits with unlabeled carbs or missing bolts – you’ll waste time sourcing replacements. Reputable brands such as BikeBerry or Grubee are consistent, though no specific model is endorsed here.

Step 3: Remove the Electric Components

Disconnect and remove everything that powered the electric motor. This includes:

1. Battery pack – Slide it out of its mount. Keep the mount if you plan to reuse it as a storage tray.

2. Hub motor or mid-drive motor – For a hub motor, loosen the axle nuts and slide the wheel out. Replace it with a standard wheel from an old bike (or buy a 26″/700c wheel with a freehub). For a mid-drive, unscrew the motor from the bottom bracket and install a standard bottom bracket and crankset.

3. Controller, wiring, and display – Snip zip ties and slide off the controller. Unplug the display and throttle. You can leave the wiring harness in place if it doesn’t interfere with the new engine; otherwise, remove it entirely.

4. Pedal-assist sensor and brake cutoffs – Magnet ring on the crank spindle and brake levers with wiring can be removed. Standard brake levers will be needed later.

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Step 4: Install the Gas Engine and Fuel Tank

1. Mount the engine – Slide the engine bracket around the downtube (or bottom bracket area, depending on kit) and tighten bolts evenly. The engine should sit parallel to the frame, with the drive sprocket aligned with the rear wheel sprocket.

2. Attach the fuel tank – Most kits include a tank that straps to the top tube. Position it so the fuel line runs down without sharp bends. Secure it with the provided rubber straps.

3. Mount the exhaust – Two-stroke kits come with a small expansion chamber. Bolt it to the engine exhaust port and route the pipe away from the rear tire and your leg. Use high-temp RTV gasket sealant on the joint to prevent leaks.

4. Install the carburetor and air filter – The carb usually bolts to the intake manifold. Attach the fuel line from the tank and check for kinks. The air filter screws onto the carb intake.

Step 5: Connect Controls and Drivetrain

1. Chain and sprockets – Remove the rear wheel’s existing freewheel or cassette. Install the kit’s large sprocket on the left side (or right, depending on kit orientation). Reinstall the wheel. Run the chain from the engine’s small drive sprocket to the large rear sprocket. Adjust tension so there’s about ½ inch of play midway.

2. Throttle cable – Screw the twist grip onto the handlebar. Route the cable to the carburetor and attach the barrel end into the throttle slide. Adjust the knuckle so the slide lifts fully when you twist fully.

3. Clutch lever – Most two-stroke kits use a manual pull-start and a centrifugal clutch, so no hand clutch is needed. If your kit has a manual clutch cable, attach it to the left brake lever housing using the kit’s small aluminum lever adapter.

Step 6: Safety Checks and Legal Considerations

• Helmet – Any bike capable of 30+ mph demands a proper helmet. Consider a certified e-bike helmet like the JARSH Commute Smart EBike Helmet with Lights (NTA-8776 rated for speeds up to 28 mph) – though your gas bike may exceed that, a DOT motorcycle helmet offers more protection.
• Brakes – Replace any worn pads. Consider installing a larger front disc rotor (203 mm) for better stopping power.
• Lights – A gas bike is effectively a moped in many jurisdictions. Add a front headlight and rear reflector. Some states require turn signals.
• Registration – In most U.S. states, a gas-powered bicycle with a motor over 49cc or capable of over 20 mph must be registered as a motor vehicle. Check your local DMV for moped or motorcycle requirements. Failure to register can result in impound and fines.

Step 7: Break-In and Tune

1. Fuel mix – Two-stroke engines need a 32:1 or 40:1 gas-to-oil ratio (check your kit manual). Use high-quality synthetic oil.

2. First start – Fill the tank, turn on the fuel valve (if present), pull the starter cord gently until resistance, then pull sharply. Let the engine idle for 2–3 minutes.

3. Carburetor adjustment – After the break-in period (about 200 miles), adjust the idle speed screw and air/fuel mixture screw. The engine should idle smoothly and accelerate without bogging. Turn the mixture screw in small increments (1/8 turn) until the engine runs clean.

4. Chain stretch – Re-tension the chain after the first 50 miles. A loose chain can skip sprockets and cause a crash.

When to Stop and Call It

If you encounter any of the following issues during the build, stop and reassess before proceeding further:

• Frame cracking or bending when you tighten the engine mount clamps – this means the frame is too weak for the vibration. Stop immediately; continuing will lead to a catastrophic frame failure at speed.
• Engine sprocket and rear sprocket are more than 1/8 inch out of alignment – you cannot fix this with chain angle. The chain will derail and lock the rear wheel. You need a different mounting bracket or frame.
• Fuel leaks from any connection – do not attempt to start the engine. Gasoline on a hot exhaust or your leg is a fire hazard. Replace the fuel line or tighten clamps first.
• Chain rubs against the frame or tire – this will cut through the frame tubing within miles. You need a different sprocket offset or a chain tensioner with a guide wheel.

If you cannot resolve these problems with basic hand tools, take the bike to a small-engine shop or abandon the conversion. Riding a gas bike with structural damage or misaligned drivetrain is dangerous.

How to Confirm the Conversion Worked

Before your first real ride, run through this success check:

1. Start and idle test: The engine should start within 3–5 pulls when cold. It should idle steadily for 60 seconds without dying or surging.

2. No fuel or exhaust leaks: After idling for 2 minutes, wipe a paper towel along every fuel line connection and the exhaust joint. Any wet spot means a leak that needs fixing.

3. Chain tracking: Pedal the bike forward 10 feet with the engine off. The chain should stay centered on both sprockets and not touch the frame, tire, or chainstay.

4. Brake test at walking speed: Ride at a slow walking pace (3–5 mph) and squeeze both brakes firmly. The bike should stop within 6 feet without pulling to one side.

5. Throttle response: From idle, twist the throttle fully open and release. The engine should rev up smoothly and return to idle without hanging at high RPM for more than 2 seconds.

If all five checks pass, the conversion is safe for a break-in ride. If any check fails, fix the issue before riding faster than 10 mph.

FAQ

Is it legal to convert an electric bike to gas?

It depends on your state. Many states classify any bike with a gas engine that can exceed 20 mph or has a motor over 50cc as a moped or motorcycle. You may need a driver’s license, registration, insurance, and safety equipment (mirrors, horn, lights). Check your state’s motor vehicle laws before riding on public roads.

Can I keep my electric bike’s pedal assist and add a gas engine?

No – the weight and mounting of a gas engine will interfere with the electric motor and battery. You must fully remove the electric drivetrain. The pedals remain, but they become purely for human power when the engine is off.

Will a conversion void my e-bike warranty?

Yes. Cutting, drilling, or clamping to the frame will void the manufacturer’s warranty. The conversion is irreversible.

How much does the conversion cost?

A basic two-stroke kit is $80–$150. Add $20–$50 for fuel, oil, tools, and possibly a new rear wheel. Total under $200 if you already have wrenches.

How fast will it go?

A 49cc two-stroke on a 26″ bike with a 44-tooth sprocket typically reaches 25–28 mph on flat ground. An 80cc can reach 30–35 mph. Gearing changes (smaller rear sprocket) can increase top speed but reduce hill-climbing ability.