What You Need to Know Before Starting
Replacing a carburetor is a job you can do at home with basic hand tools and about an hour of time. The carburetor mixes fuel and air so your engine can run, and when it gets clogged or fails, the engine won't start or runs rough. You'll need to drain the fuel tank first, disconnect the old carburetor, install the new one, and reconnect the fuel and air lines in reverse order.
This guide covers small engines—lawn mowers, generators, pressure washers, and similar equipment. Larger engines in cars and trucks use different procedures and may require specialized tools. If you're working on a vehicle, consult the manufacturer's manual or a mechanic instead.
Key Takeaways
- Drain the fuel tank completely before you start, or fuel will spill when you disconnect the carburetor.
- Take a photo of the fuel line, throttle cable, and choke cable before you remove them so you know where each one reconnects.
- The new carburetor may come with a gasket already attached, but check your old one first to see if you need to transfer it or buy a replacement.
- Tighten the mounting bolts by hand first, then use a wrench to snug them—over-tightening can crack the carburetor body.
- Fill the fuel tank halfway and test the engine before you close up the equipment, in case you need to adjust the fuel line or choke cable.
Gather Your Tools and Parts
You'll need a socket set or wrench set that fits your engine's bolts, a screwdriver (usually Phillips head), a fuel line clamp or hose clamp, and a small container to catch any fuel that drips. Have a clean rag nearby—carburetor work gets messy.
Before you buy a replacement carburetor, confirm the exact model and year of your equipment. The model number is usually stamped on the engine block or printed on a sticker. Order a carburetor that matches your engine's specifications exactly. Some carburetors come with a gasket and fuel line already attached; others don't. Check what's included so you don't end up missing a part halfway through.
Drain the Fuel Tank and Disconnect the Lines
Turn off the engine and let it cool for at least 15 minutes. Locate the fuel tank drain plug—it's usually a small bolt at the lowest point of the tank. Place your container underneath and turn the plug counterclockwise by hand or with a wrench. Let all the fuel drain out completely. This step prevents fuel from spilling onto your work surface and into the carburetor.
Once the tank is empty, locate the fuel line that runs from the tank to the carburetor. It's usually a rubber hose about the thickness of a pencil. Loosen the hose clamp that holds it to the carburetor with a screwdriver, then gently pull the hose free. If fuel drips out, catch it with your rag. Do the same for any other lines connected to the carburetor—some engines have a return line that goes back to the tank.
Remove the Throttle and Choke Cables
Before you touch the carburetor itself, photograph the throttle cable and choke cable where they attach. These cables control how much fuel flows into the engine and how the engine starts when it's cold. The cables are usually held on with a small bolt or a clip.
Loosen the bolt or unclip the cable from the carburetor arm. Don't pull the cable all the way out of the engine housing—just disconnect it from the carburetor. You'll reconnect it to the new carburetor in the same position. If the cable is stuck or corroded, spray it lightly with penetrating oil and wait a few minutes before trying again.
Unbolt and Remove the Old Carburetor
The carburetor is held to the engine with two or four bolts that run through a mounting flange. Use your socket wrench to turn these bolts counterclockwise. Start with the bolts on opposite sides so the carburetor doesn't tilt and bind. Once all bolts are loose, lift the carburetor straight up and away from the engine.
Look at the gasket—the thin rubber or cork seal between the carburetor and the engine. If it's still in good condition and came with your new carburetor, you can reuse it. If it's cracked, compressed, or your new carburetor didn't come with one, you'll need to buy a replacement gasket that matches your engine model. Scrape off any old gasket material from the engine mounting surface with a plastic scraper or old credit card, then wipe the surface clean with a dry rag.
Install the New Carburetor
Place the new gasket on the engine mounting surface, then lower the new carburetor onto it. Insert the mounting bolts by hand first and turn them clockwise until they're snug—don't use the wrench yet. This lets the carburetor settle into position without binding. Once all bolts are hand-tight, use your wrench to tighten them in a crisscross pattern (top-left, bottom-right, top-right, bottom-left) so the carburetor sits evenly. Tighten each bolt only a quarter turn at a time until they're snug. Over-tightening can crack the carburetor body.
Reconnect the fuel line to the carburetor inlet port—it's usually labeled or is the larger of the two ports. Slide the hose onto the fitting and tighten the hose clamp with your screwdriver. Don't over-tighten; you just need it tight enough that the hose won't slip off when the engine runs.
Reconnect the Throttle and Choke Cables
Use your photo as a guide to reconnect the throttle cable to the carburetor arm in the same position it was before. The cable should have a small amount of slack when the throttle is at rest—not tight, but not drooping either. Tighten the bolt or clip that holds it in place.
Do the same for the choke cable. When you pull the choke handle on the engine, the cable should move smoothly without binding. If the cable feels stiff or won't move all the way, loosen the connection and adjust the cable position slightly, then tighten it again. Test the movement by hand before you start the engine.
Test the Engine and Adjust as Needed
Fill the fuel tank halfway with fresh fuel. Turn on the fuel valve (if your engine has one) and wait 10 seconds for fuel to reach the carburetor. Set the choke to the cold-start position and pull the starter cord. The engine should start within three pulls. If it doesn't, check that the fuel line is connected and the choke cable moves freely.
Once the engine starts, let it run for two minutes while you watch for fuel leaks around the carburetor and fuel line connections. If you see fuel dripping, turn off the engine when ready, let it cool, and tighten the leaking connection. If the engine runs smoothly and there are no leaks, you're done. If the engine runs rough or won't idle, the carburetor may need adjustment—consult your engine's manual for idle speed and fuel mixture settings.
Frequently Asked Questions
Do I need to buy a new gasket or can I reuse the old one?
If the old gasket is still flexible and hasn't been compressed flat, you can reuse it. If it's cracked, hard, or flattened, buy a new one that matches your engine model. A bad gasket will cause fuel leaks and air leaks that make the engine run poorly.
What if the new carburetor comes with a fuel line already attached?
Some replacement carburetors include a pre-attached fuel line. If yours does, disconnect the old line from the tank and connect the new line instead. Make sure the line is long enough to reach the tank without kinking or stretching.
Can I clean the old carburetor instead of replacing it?
Yes, if the carburetor is clogged with old fuel varnish, you can soak it in carburetor cleaner for several hours and blow out the passages with compressed air. However, if the carburetor is cracked, the needle valve is worn, or the float is damaged, cleaning won't fix it and replacement is the better choice.
How tight should the mounting bolts be?
Tighten them until they're snug and the carburetor doesn't move, but stop before you feel strong resistance. Carburetor bodies are made of aluminum or plastic and crack easily if over-tightened. If you're using a torque wrench, most small engines call for 5 to 8 foot-pounds.
What should I do with the old carburetor?
If it's still intact, you can keep it as a spare or sell it online. If it's cracked or damaged beyond repair, check with your local waste management facility about how to dispose of it—some accept small engine parts at recycling centers.