Few things are as frustrating as pulling the cord on your trimmer or blower and getting nothing but sputtering, coughing, or silence. In small engines, especially after long storage periods, the main culprit is almost always the carburetor, which has been fouled by stale, ethanol-laced gasoline.
When your engine is surging, stalling, or struggling to maintain a consistent idle, it’s time for some focused carburetor cleaning.
🧐 Step 1: Diagnosing the Problem
Before tearing the engine apart, confirm the issue is fuel-related:
- Hard Starting: The engine might fire briefly then die, or require excessive choking. This suggests the pilot jet (idle circuit) is partially blocked.
- Surging or Hunting: The engine speeds up and slows down rhythmically, often under no load. This usually points to a partially blocked main jet or a vacuum leak.
- No Start: If you have spark and fresh fuel, the entire carburetor is likely blocked, preventing any fuel from entering the engine.
Crucial Note: Modern ethanol gas attracts moisture, forming a gummy, varnish-like residue when it evaporates. This residue clogs the tiny, precisely sized passageways inside the carburetor.
🔧 Step 2: The Carburetor Cleaning Procedure
While professional shops often use ultrasonic cleaners, you can achieve excellent results at home with the right tools and patience.
1. Disassembly and Inspection
- Safely Drain the Fuel: Empty the tank and fuel lines of all old fuel.
- Remove the Carburetor: Carefully disconnect the air filter housing, throttle linkage, and fuel line. Take pictures! Use your phone to document the precise location of all springs and linkages before removal.
- Open the Bowl (If Applicable): For carburetors with a float bowl, remove the retaining screw to access the float and float needle. Ensure the float moves freely and the needle (which seals off the fuel inlet) is not stuck.
2. Cleaning the Jets and Passageways
The jets are the brass screws or inserts that regulate fuel flow. They are the most crucial, and often most clogged, parts.
- Remove the Jets: Use the correct screwdriver to remove the main jet and idle jet. Be careful—they are soft and easily damaged.
- Use Carburetor Cleaner: Spray non-chlorinated carburetor cleaner into every hole, port, and passageway you can find, focusing heavily on the empty jet bores. You should see a powerful stream of cleaner exit through another passage.
- Use Compressed Air: Follow the liquid cleaner with a strong blast of compressed air (or use a can of compressed air). This helps ensure all dissolved varnish is physically blown out of the microscopic holes.
- Re-Check the Jets: Visually hold the removed jets up to a light. The tiny central hole must be perfectly clear and round. You can gently use a thin strand of wire from a wire brush to push through the holes, but never drill or enlarge them.
3. Replacing the Gaskets
Small engine carbs use thin rubber and paper gaskets and seals. These dry out, crack, and lose their sealing ability when exposed to old fuel.
- Recommendation: When cleaning a severely clogged carburetor, it is highly recommended to install a carburetor kit. These kits are inexpensive and include a new float needle, gaskets, and sometimes new jets, ensuring a proper seal upon reassembly.
✅ Step 3: Prevention for the Future
To prevent this frustrating cycle of cleaning, remember these two rules:
- Use Stabilizer: Add a quality fuel stabilizer (like STA-BIL) to every can of mixed fuel you make, not just the batch you plan to store.
- Run It Dry: At the end of the season, or if you plan to store the equipment for more than a month, run the engine until it completely runs out of fuel and stalls. This ensures there is no standing, varnish-forming fuel left in the carburetor bowl or jets.