Nine times out of ten, a mower, trimmer or generator that cranks but won't start has one of three problems: stale fuel in the carburetor, a worn spark plug, or a broken recoil starter. Here's the order a small-engine shop would check them in — and what's worth replacing yourself.
Start with fuel (it's usually fuel)
Petrol left in the tank over winter oxidises and gums up the carburetor's tiny jets. Symptoms: engine fires briefly on starter fluid then dies, surges at idle, or won't idle without choke. Two fixes:
- Clean: remove the bowl, spray carb cleaner through the main jet, replace the bowl gasket.
- Replace: aftermarket carburetors for common Briggs & Stratton, Honda-clone, Predator, Cub Cadet and Echo engines typically cost less than a repair-shop hour. Match by engine model number (stamped on the blower housing or valve cover), not by the machine's brand name — the same mower brand can use three different engines across model years.
Spark: the 2-minute test
Pull the plug, clip it back into its boot, ground the threads against the engine block and pull the cord. A healthy plug throws a visible blue spark. Weak orange spark or nothing → replace the plug first (cheap), then the ignition coil if there's still no spark. Gap the new plug to your engine's spec — pre-gapped isn't always right.
Recoil starters: fix or swap?
If the cord won't retract or pulls out limp, the recoil spring has let go. Rewinding a spring is doable but fiddly; complete recoil assemblies for Echo, Stihl-pattern and generator engines bolt on in ten minutes with four screws. Again — match by engine model, and check the OEM part number cross-reference in the listing.
The 10-minute pre-season routine that prevents all this
- Run the tank dry (or add stabiliser) before storage.
- New plug + clean air filter every spring.
- Fresh fuel only — ethanol-free if your engine allows it.
- Pull the cord slowly once a month off-season to keep the recoil spring live.
Quick answers
How do I find my engine model number? On mowers it's usually stamped above the spark plug or on the blower housing; on generators, on a plate near the recoil. Photograph it before ordering parts.
Are aftermarket carburetors any good? For homeowner machines, quality aftermarket carbs (with fresh gaskets included) are the standard budget fix — they're often identical castings to OEM.
Why does my engine only run on choke? A partially blocked main jet — clean or replace the carburetor.
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General information for US homeowners, not professional or product-specific advice. Always follow the manufacturer’s manual and, for lawn-care products, the EPA-registered label instructions.
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